Pipe Schedule Chart: NPS, DN, OD, ID & Wall Thickness

Name: Aienginear Pipe Size and Schedule Chart (NPS 1/8 to 48)
Creator: Muhammad Raza
License: https://aienginear.com/pipe-sizes-schedule/

Quick answer

Pipe size is stated as a nominal size – NPS (inches) or DN (metric) – plus a wall designation such as Sch 40, Sch 80 or 40S. The nominal size fixes the outside diameter (OD); the schedule fixes the wall thickness. The bore is therefore ID = OD − 2 × wall. Example: NPS 2 Sch 40 = 2.375 in OD, 0.154 in wall, 2.067 in ID (60.3 / 3.91 / 52.5 mm). The complete pipe schedule chart, NPS to DN table and calculator are below.

Table of Contents

NPS ⅛ – 12OD is a fixed value larger than the nominal size (NPS 6 = 6.625 in OD).

NPS 14 and upOD equals the nominal size exactly (NPS 14 = 14.000 in OD).

Schedule ≠ pressure ratingWall must be checked with ASME B31.1 / B31.3 and the material allowable stress.

40 vs 40SIdentical up to NPS 10, different from NPS 12 upward – check before you order stainless.

Standards used in this guide (reviewed October 2026)

ASME B36.10-2022 – Welded and Seamless Wrought Steel Pipe (dimensions, schedules, STD/XS/XXS, mass formula).
ASME B36.19M-2018 – Stainless Steel Pipe (5S, 10S, 40S, 80S).
ASTM A530/A530M – General requirements for specialized carbon and alloy steel pipe (dimensional tolerances).
ISO 6708 – Definition of DN; EN 10220 / ISO 4200 – European OD series (for comparison).
ASME B31.3 / B31.1 – Process and power piping codes that decide the required wall.

Video – Pipe sizes and pipe schedules explained (Aienginear on YouTube).

What Is Nominal Pipe Size (NPS)?

Nominal Pipe Size (NPS) is the North American size designation for pipe. It is a label, not a measurement: a "6-inch pipe" is NPS 6, whose real outside diameter is 6.625 in and whose bore depends on the wall thickness you choose. The system descends from the old Iron Pipe Size (IPS) practice, where the nominal figure roughly matched the bore of standard-weight pipe.

The key idea for every piping engineer: for a given NPS the OD never changes. Mills hold the OD constant so that fittings, flanges, clamps and supports fit every schedule of that size. When the wall gets thicker, the material grows inward and the ID shrinks.

Figure 1 – OD, ID and wall thickness. Only OD and wall are specified; ID is the result.

Why NPS Matches Neither OD nor ID Below NPS 14

From NPS ⅛ to NPS 12 the OD is a fixed historical value that is larger than the nominal number, so the nominal size falls somewhere between the ID and OD. From NPS 14 (DN 350) upward the OD is exactly equal to the NPS in inches. The table below shows both behaviours side by side.

AIENGINEARNPS 2 vs NPS 14 – Sch 40 dimensions

Pipe	OD (in)	OD (mm)	Wall (in)	Wall (mm)	ID (in)	ID (mm)	Observation
NPS 2 Sch 40	2.375	60.3	0.154	3.91	2.067	52.5	ID ≈ NPS
NPS 14 Sch 40	14.000	355.6	0.438	11.13	13.124	333.3	OD = NPS

NPS 2 OD is 2.375 in but its Sch 40 bore is 2.067 in (close to the nominal 2). NPS 14 OD is exactly 14.000 in. Source: Aienginear compilation per ASME B36.10-2022 (welded & seamless wrought steel pipe) and ASME B36.19M (stainless steel pipe). – = no standard wall for that schedule. Verify against the edition named in your project specification.

Figure 2 – Small-bore vs large-bore sizing rule.

Converting inch dimensions to millimetres

Multiply by 25.4, then round the way ASME B36.10 does: OD of NPS 16 and smaller to the nearest 0.1 mm, larger ODs to the nearest 1 mm, and wall thickness to the nearest 0.01 mm. That is why NPS 18 is listed as 457 mm (not 457.2) and NPS 2 as 60.3 mm.

NPS vs NB vs DN – What Is the Difference?

NB (Nominal Bore) is the British/Asian shop-floor name for the same thing as NPS – "2 inch NB" and "NPS 2" describe the same pipe. DN (Diamètre Nominal) is the dimensionless metric designator defined in ISO 6708. DN is not a millimetre measurement: DN 50 has an OD of 60.3 mm and a Sch 40 bore of 52.5 mm.

A fast rule is DN ≈ NPS × 25, but the exceptions trip people up: NPS 1¼ = DN 32, NPS 1½ = DN 40, NPS 2½ = DN 65, NPS 3½ = DN 90 and NPS 5 = DN 125. Nominal sizes step by ¼ in and ½ in up to NPS 4, then NPS 5 and 6, then by 2 in from NPS 6 to NPS 48, and by 4 in for the larger B36.10 sizes up to NPS 80. Use the filterable chart instead of mental arithmetic.

AIENGINEARNPS to DN and Outside Diameter (OD) Master Chart

NPS (in)	DN	OD (in)	OD (mm)	OD rule
⅛	6	0.405	10.3	OD fixed, larger than NPS
¼	8	0.540	13.7	OD fixed, larger than NPS
⅜	10	0.675	17.1	OD fixed, larger than NPS
½	15	0.840	21.3	OD fixed, larger than NPS
¾	20	1.050	26.7	OD fixed, larger than NPS
1	25	1.315	33.4	OD fixed, larger than NPS
1¼	32	1.660	42.2	OD fixed, larger than NPS
1½	40	1.900	48.3	OD fixed, larger than NPS
2	50	2.375	60.3	OD fixed, larger than NPS
2½	65	2.875	73.0	OD fixed, larger than NPS
3	80	3.500	88.9	OD fixed, larger than NPS
3½	90	4.000	101.6	OD fixed, larger than NPS
4	100	4.500	114.3	OD fixed, larger than NPS
5	125	5.563	141.3	OD fixed, larger than NPS
6	150	6.625	168.3	OD fixed, larger than NPS
8	200	8.625	219.1	OD fixed, larger than NPS
10	250	10.750	273.0	OD fixed, larger than NPS
12	300	12.750	323.8	OD fixed, larger than NPS
14	350	14.000	355.6	OD = NPS (inch)
16	400	16.000	406.4	OD = NPS (inch)
18	450	18.000	457.0	OD = NPS (inch)
20	500	20.000	508.0	OD = NPS (inch)
22	550	22.000	559.0	OD = NPS (inch)
24	600	24.000	610.0	OD = NPS (inch)
26	650	26.000	660.0	OD = NPS (inch)
28	700	28.000	711.0	OD = NPS (inch)
30	750	30.000	762.0	OD = NPS (inch)
32	800	32.000	813.0	OD = NPS (inch)
34	850	34.000	864.0	OD = NPS (inch)
36	900	36.000	914.0	OD = NPS (inch)
38	950	38.000	965.0	OD = NPS (inch)
40	1000	40.000	1016.0	OD = NPS (inch)
42	1050	42.000	1067.0	OD = NPS (inch)
44	1100	44.000	1118.0	OD = NPS (inch)
46	1150	46.000	1168.0	OD = NPS (inch)
48	1200	48.000	1219.0	OD = NPS (inch)

DN designations per ISO 6708 / ASME B36.10 Table 2-1. OD is constant for every schedule of a given NPS. Sizes NPS 52–80 (DN 1300–2000) are also covered by ASME B36.10 with OD = NPS. Source: Aienginear compilation per ASME B36.10-2022 (welded & seamless wrought steel pipe) and ASME B36.19M (stainless steel pipe). – = no standard wall for that schedule. Verify against the edition named in your project specification.

Same DN, Different OD: ASME vs European Pipe

On international projects you will meet pipe to EN 10220 / ISO 4200. Most ODs match ASME, but a few do not – and a 3 mm OD mismatch means butt-weld fittings, flanges and clamps will not fit. Always state the dimensional standard, not just the DN.

AIENGINEARDN Outside Diameter: ASME B36.10 vs EN 10220 / ISO 4200 (Series 1)

DN	ASME OD (mm)	EN 10220 OD (mm)	Compatibility
15	21.3	21.3	Same
20	26.7	26.9	Minor (≤0.3 mm) – normally interchangeable
25	33.4	33.7	Minor (≤0.3 mm) – normally interchangeable
32	42.2	42.4	Minor (≤0.3 mm) – normally interchangeable
40	48.3	48.3	Same
50	60.3	60.3	Same
65	73.0	76.1	Different – check fittings & flanges
80	88.9	88.9	Same
100	114.3	114.3	Same
125	141.3	139.7	Different – check fittings & flanges
150	168.3	168.3	Same
200	219.1	219.1	Same
250	273.0	273.0	Same
300	323.8	323.9	Minor (≤0.3 mm) – normally interchangeable
350	355.6	355.6	Same
400	406.4	406.4	Same
450	457.0	457.0	Same
500	508.0	508.0	Same
600	610.0	610.0	Same

The same DN does not always mean the same OD. DN 65 (73.0 vs 76.1 mm) and DN 125 (141.3 vs 139.7 mm) are the classic mismatches when mixing American and European pipe, fittings and flanges.

What Is a Pipe Schedule?

A pipe schedule is a standardized designation for wall thickness. Early wrought-iron pipe came in only three weights – Standard (STD), Extra Strong (XS) and Double Extra Strong (XXS). As steam, refinery and petrochemical pressures rose, three steps became too coarse, so the ASA (now ASME) committee introduced schedule numbers from 5 to 160. Their origin is an approximate ratio:

Schedule No. ≈ 1000 × P / S (P = service pressure, psi; S = allowable stress, psi)

Today that formula is only history. The actual wall for each schedule is a tabulated value in ASME B36.10, and the same schedule number gives a different absolute wall at each size. What stays true is that, for the same NPS, a higher schedule means a thicker wall and a smaller bore. A schedule number is not a pressure rating – that comes from the piping code calculation shown later in this guide.

Figure 3 – NPS 4 (DN 100): wall thickness rises from 2.11 mm (Sch 5S) to 17.12 mm (XXS) while the OD stays 114.3 mm.

STD, XS and XXS vs Schedule Numbers

The legacy weight classes are still everywhere on drawings and in ASTM A53/A106 orders. STD equals Sch 40 only up to NPS 10, and XS equals Sch 80 only up to NPS 8. Above those sizes they remain at 0.375 in and 0.500 in respectively, while Sch 40 and Sch 80 keep growing. XXS has no consistent schedule equivalent.

AIENGINEARWeight Classes STD, XS and XXS vs Schedule Numbers

NPS	DN	STD (Standard)	XS (Extra Strong)	XXS (Double Extra Strong)
⅛	6	0.068 in / 1.73 mm (= Sch 40)	0.095 in / 2.41 mm (= Sch 80)	–
¼	8	0.088 in / 2.24 mm (= Sch 40)	0.119 in / 3.02 mm (= Sch 80)	–
⅜	10	0.091 in / 2.31 mm (= Sch 40)	0.126 in / 3.20 mm (= Sch 80)	–
½	15	0.109 in / 2.77 mm (= Sch 40)	0.147 in / 3.73 mm (= Sch 80)	0.294 in / 7.47 mm
¾	20	0.113 in / 2.87 mm (= Sch 40)	0.154 in / 3.91 mm (= Sch 80)	0.308 in / 7.82 mm
1	25	0.133 in / 3.38 mm (= Sch 40)	0.179 in / 4.55 mm (= Sch 80)	0.358 in / 9.09 mm
1¼	32	0.140 in / 3.56 mm (= Sch 40)	0.191 in / 4.85 mm (= Sch 80)	0.382 in / 9.70 mm
1½	40	0.145 in / 3.68 mm (= Sch 40)	0.200 in / 5.08 mm (= Sch 80)	0.400 in / 10.15 mm
2	50	0.154 in / 3.91 mm (= Sch 40)	0.218 in / 5.54 mm (= Sch 80)	0.436 in / 11.07 mm
2½	65	0.203 in / 5.16 mm (= Sch 40)	0.276 in / 7.01 mm (= Sch 80)	0.552 in / 14.02 mm
3	80	0.216 in / 5.49 mm (= Sch 40)	0.300 in / 7.62 mm (= Sch 80)	0.600 in / 15.24 mm
3½	90	0.226 in / 5.74 mm (= Sch 40)	0.318 in / 8.08 mm (= Sch 80)	0.636 in / 16.15 mm
4	100	0.237 in / 6.02 mm (= Sch 40)	0.337 in / 8.56 mm (= Sch 80)	0.674 in / 17.12 mm
5	125	0.258 in / 6.55 mm (= Sch 40)	0.375 in / 9.53 mm (= Sch 80)	0.750 in / 19.05 mm
6	150	0.280 in / 7.11 mm (= Sch 40)	0.432 in / 10.97 mm (= Sch 80)	0.864 in / 21.95 mm
8	200	0.322 in / 8.18 mm (= Sch 40)	0.500 in / 12.70 mm (= Sch 80)	0.875 in / 22.23 mm
10	250	0.365 in / 9.27 mm (= Sch 40)	0.500 in / 12.70 mm (= Sch 60)	1.000 in / 25.40 mm (= Sch 140)
12	300	0.375 in / 9.53 mm	0.500 in / 12.70 mm	1.000 in / 25.40 mm (= Sch 120)
14	350	0.375 in / 9.53 mm (= Sch 30)	0.500 in / 12.70 mm	–
16	400	0.375 in / 9.53 mm (= Sch 30)	0.500 in / 12.70 mm (= Sch 40)	–
18	450	0.375 in / 9.53 mm	0.500 in / 12.70 mm	–
20	500	0.375 in / 9.53 mm (= Sch 20)	0.500 in / 12.70 mm (= Sch 30)	–
22	550	0.375 in / 9.53 mm (= Sch 20)	0.500 in / 12.70 mm (= Sch 30)	–
24	600	0.375 in / 9.53 mm (= Sch 20)	0.500 in / 12.70 mm	–
26	650	0.375 in / 9.53 mm	0.500 in / 12.70 mm (= Sch 20)	–
28	700	0.375 in / 9.53 mm	0.500 in / 12.70 mm (= Sch 20)	–
30	750	0.375 in / 9.53 mm	0.500 in / 12.70 mm (= Sch 20)	–
32	800	0.375 in / 9.53 mm	0.500 in / 12.70 mm (= Sch 20)	–
34	850	0.375 in / 9.53 mm	0.500 in / 12.70 mm (= Sch 20)	–
36	900	0.375 in / 9.53 mm	0.500 in / 12.70 mm (= Sch 20)	–
38	950	0.375 in / 9.53 mm	0.500 in / 12.70 mm	–
40	1000	0.375 in / 9.53 mm	0.500 in / 12.70 mm	–
42	1050	0.375 in / 9.53 mm	0.500 in / 12.70 mm	–
44	1100	0.375 in / 9.53 mm	0.500 in / 12.70 mm	–
46	1150	0.375 in / 9.53 mm	0.500 in / 12.70 mm	–
48	1200	0.375 in / 9.53 mm	0.500 in / 12.70 mm	–

STD equals Sch 40 up to NPS 10; XS equals Sch 80 up to NPS 8. Above those sizes STD stays at 0.375 in (9.53 mm) and XS at 0.500 in (12.70 mm). Source: Aienginear compilation per ASME B36.10-2022 (welded & seamless wrought steel pipe) and ASME B36.19M (stainless steel pipe). – = no standard wall for that schedule. Verify against the edition named in your project specification.

ASME B36.10 vs ASME B36.19M (Carbon Steel vs Stainless Steel)

Stainless steel resists corrosion, so it rarely needs a corrosion allowance – and it is expensive. ASME B36.19M therefore defines lighter "S" schedules (5S, 10S, 40S, 80S) that use the same ODs as carbon steel but optimise wall thickness for cost. Carbon and low-alloy steel pipe follows ASME B36.10.

AIENGINEARASME B36.10 vs ASME B36.19M at a Glance

Item	ASME B36.10	ASME B36.19M
Title	Welded and Seamless Wrought Steel Pipe	Stainless Steel Pipe
Current edition	ASME B36.10-2022 (supersedes B36.10M-2018)	ASME B36.19M-2018 (check for later edition)
Typical materials	Carbon, C-Mn, low-alloy steels (A53, A106, A333, A335, API 5L)	Austenitic, duplex and other stainless steels (A312, A358, A790)
Size range	NPS ⅛ to 80 (DN 6–2000)	NPS ⅛ to 30 (DN 6–750)
Wall designations	Sch 5*, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160; STD, XS, XXS	Sch 5S, 10S, 40S, 80S
Outside diameters	Common OD series	Same OD series as B36.10
Why it exists	Pressure, mechanical strength and corrosion allowance for carbon steel	Thinner, cost-effective walls – stainless needs little or no corrosion allowance

*Light-wall Sch 5 sizes are listed in many carbon-steel charts; confirm the exact designation in the edition you specify.

When Sch 40 Is Not Sch 40S

This is one of the most common requisition errors we see during project material take-offs. Up to NPS 10 the numbers match; from NPS 12 they diverge:

AIENGINEARWhere Schedule 10/40/80 and 10S/40S/80S Are NOT the Same

NPS	DN	ASME B36.10	ASME B36.19M	S-schedule is
10	250	Sch 80: 0.594 in (15.09 mm)	Sch 80S: 0.500 in (12.70 mm)	2.39 mm thinner
12	300	Sch 40: 0.406 in (10.31 mm)	Sch 40S: 0.375 in (9.53 mm)	0.79 mm thinner
12	300	Sch 80: 0.688 in (17.48 mm)	Sch 80S: 0.500 in (12.70 mm)	4.78 mm thinner
14	350	Sch 10: 0.250 in (6.35 mm)	Sch 10S: 0.188 in (4.78 mm)	1.57 mm thinner
14	350	Sch 40: 0.438 in (11.13 mm)	Sch 40S: 0.375 in (9.53 mm)	1.60 mm thinner
14	350	Sch 80: 0.750 in (19.05 mm)	Sch 80S: 0.500 in (12.70 mm)	6.35 mm thinner
16	400	Sch 10: 0.250 in (6.35 mm)	Sch 10S: 0.188 in (4.78 mm)	1.57 mm thinner
16	400	Sch 40: 0.500 in (12.70 mm)	Sch 40S: 0.375 in (9.53 mm)	3.17 mm thinner
16	400	Sch 80: 0.844 in (21.44 mm)	Sch 80S: 0.500 in (12.70 mm)	8.74 mm thinner
18	450	Sch 10: 0.250 in (6.35 mm)	Sch 10S: 0.188 in (4.78 mm)	1.57 mm thinner
18	450	Sch 40: 0.562 in (14.27 mm)	Sch 40S: 0.375 in (9.53 mm)	4.75 mm thinner
18	450	Sch 80: 0.938 in (23.83 mm)	Sch 80S: 0.500 in (12.70 mm)	11.13 mm thinner
20	500	Sch 10: 0.250 in (6.35 mm)	Sch 10S: 0.218 in (5.54 mm)	0.81 mm thinner
20	500	Sch 40: 0.594 in (15.09 mm)	Sch 40S: 0.375 in (9.53 mm)	5.56 mm thinner
20	500	Sch 80: 1.031 in (26.19 mm)	Sch 80S: 0.500 in (12.70 mm)	13.49 mm thinner
22	550	Sch 10: 0.250 in (6.35 mm)	Sch 10S: 0.218 in (5.54 mm)	0.81 mm thinner
24	600	Sch 40: 0.688 in (17.48 mm)	Sch 40S: 0.375 in (9.53 mm)	7.95 mm thinner
24	600	Sch 80: 1.219 in (30.96 mm)	Sch 80S: 0.500 in (12.70 mm)	18.26 mm thinner

For every size not listed, 10 = 10S, 40 = 40S and 80 = 80S. Writing "Sch 40" on a stainless steel requisition for NPS 12 and larger can buy a heavier, more expensive wall than the designer intended. Source: Aienginear compilation per ASME B36.10-2022 (welded & seamless wrought steel pipe) and ASME B36.19M (stainless steel pipe). – = no standard wall for that schedule. Verify against the edition named in your project specification.

How to Calculate Pipe ID, Flow Area and Weight

Find the OD for the NPS/DN from the master chart (e.g. NPS 6 = 6.625 in / 168.3 mm).
Find the wall thickness for the schedule from the schedule chart (NPS 6 Sch 40 = 0.280 in / 7.11 mm).
Inside diameter: ID = OD − 2t = 6.625 − 2 × 0.280 = 6.065 in (154.1 mm).
Flow area: A = π × ID² / 4 = 28.89 in² (186.5 cm²).
Plain-end weight (carbon steel): W = 10.69 (OD − t) t = 18.99 lb/ft, or W = 0.0246615 (OD − t) t = 28.26 kg/m.
Minimum wall for design checks: t_min = 0.875 × t = 0.245 in when the purchase spec allows −12.5% mill tolerance.

Pipe Dimension & Weight Calculator (NPS ⅛ to 48)

Pick a standard size and schedule, or enter any OD and wall. The calculator returns ID, flow area, steel weight, water-filled weight, the −12.5% minimum wall and a comparison of every schedule for that size. Switching units converts your custom entries, so the physical pipe stays the same.

Aienginear Pipe Dimension CalculatorASME B36.10 / B36.19M data

Input mode

Units

Nominal size

Schedule

Material (for weight)

Complete Pipe Schedule Chart in Inches

Wall thickness in inches for every ASME schedule from NPS ⅛ to NPS 48. Type a size in the filter box (for example 6 or DN 150), hover to highlight a schedule column, or print a branded A4 copy.

AIENGINEARPipe Schedule Chart – Wall Thickness in Inches (NPS ⅛ to 48)

NPS (in)	OD (in)	5	5S	10	10S	20	30	40	40S	STD	60	80	80S	XS	100	120	140	160	XXS
⅛	0.405	–	–	0.049	0.049	–	0.057	0.068	0.068	0.068	–	0.095	0.095	0.095	–	–	–	–	–
¼	0.540	–	–	0.065	0.065	–	0.073	0.088	0.088	0.088	–	0.119	0.119	0.119	–	–	–	–	–
⅜	0.675	–	–	0.065	0.065	–	0.073	0.091	0.091	0.091	–	0.126	0.126	0.126	–	–	–	–	–
½	0.840	0.065	0.065	0.083	0.083	–	0.095	0.109	0.109	0.109	–	0.147	0.147	0.147	–	–	–	0.188	0.294
¾	1.050	0.065	0.065	0.083	0.083	–	0.095	0.113	0.113	0.113	–	0.154	0.154	0.154	–	–	–	0.219	0.308
1	1.315	0.065	0.065	0.109	0.109	–	0.114	0.133	0.133	0.133	–	0.179	0.179	0.179	–	–	–	0.250	0.358
1¼	1.660	0.065	0.065	0.109	0.109	–	0.117	0.140	0.140	0.140	–	0.191	0.191	0.191	–	–	–	0.250	0.382
1½	1.900	0.065	0.065	0.109	0.109	–	0.125	0.145	0.145	0.145	–	0.200	0.200	0.200	–	–	–	0.281	0.400
2	2.375	0.065	0.065	0.109	0.109	–	0.125	0.154	0.154	0.154	–	0.218	0.218	0.218	–	–	–	0.344	0.436
2½	2.875	0.083	0.083	0.120	0.120	–	0.188	0.203	0.203	0.203	–	0.276	0.276	0.276	–	–	–	0.375	0.552
3	3.500	0.083	0.083	0.120	0.120	–	0.188	0.216	0.216	0.216	–	0.300	0.300	0.300	–	–	–	0.438	0.600
3½	4.000	0.083	0.083	0.120	0.120	–	0.188	0.226	0.226	0.226	–	0.318	0.318	0.318	–	–	–	–	0.636
4	4.500	0.083	0.083	0.120	0.120	–	0.188	0.237	0.237	0.237	–	0.337	0.337	0.337	–	0.438	–	0.531	0.674
5	5.563	0.109	0.109	0.134	0.134	–	–	0.258	0.258	0.258	–	0.375	0.375	0.375	–	0.500	–	0.625	0.750
6	6.625	0.109	0.109	0.134	0.134	–	–	0.280	0.280	0.280	–	0.432	0.432	0.432	–	0.562	–	0.719	0.864
8	8.625	0.109	0.109	0.148	0.148	0.250	0.277	0.322	0.322	0.322	0.406	0.500	0.500	0.500	0.594	0.719	0.812	0.906	0.875
10	10.750	0.134	0.134	0.165	0.165	0.250	0.307	0.365	0.365	0.365	0.500	0.594	0.500	0.500	0.719	0.844	1.000	1.125	1.000
12	12.750	0.156	0.156	0.180	0.180	0.250	0.330	0.406	0.375	0.375	0.562	0.688	0.500	0.500	0.844	1.000	1.125	1.312	1.000
14	14.000	0.156	0.156	0.250	0.188	0.312	0.375	0.438	0.375	0.375	0.594	0.750	0.500	0.500	0.938	1.094	1.250	1.406	–
16	16.000	0.165	0.165	0.250	0.188	0.312	0.375	0.500	0.375	0.375	0.656	0.844	0.500	0.500	1.031	1.219	1.438	1.594	–
18	18.000	0.165	0.165	0.250	0.188	0.312	0.438	0.562	0.375	0.375	0.750	0.938	0.500	0.500	1.156	1.375	1.562	1.781	–
20	20.000	0.188	0.188	0.250	0.218	0.375	0.500	0.594	0.375	0.375	0.812	1.031	0.500	0.500	1.281	1.500	1.750	1.969	–
22	22.000	0.188	0.188	0.250	0.218	0.375	0.500	–	–	0.375	0.875	1.125	–	0.500	1.375	1.625	1.875	2.125	–
24	24.000	0.218	0.218	0.250	0.250	0.375	0.562	0.688	0.375	0.375	0.969	1.219	0.500	0.500	1.531	1.812	2.062	2.344	–
26	26.000	–	–	0.312	–	0.500	–	–	–	0.375	–	–	–	0.500	–	–	–	–	–
28	28.000	–	–	0.312	–	0.500	0.625	–	–	0.375	–	–	–	0.500	–	–	–	–	–
30	30.000	0.250	0.250	0.312	0.312	0.500	0.625	–	–	0.375	–	–	–	0.500	–	–	–	–	–
32	32.000	–	–	0.312	–	0.500	0.625	0.688	–	0.375	–	–	–	0.500	–	–	–	–	–
34	34.000	–	–	0.312	–	0.500	0.625	0.688	–	0.375	–	–	–	0.500	–	–	–	–	–
36	36.000	–	–	0.312	–	0.500	0.625	0.750	–	0.375	–	–	–	0.500	–	–	–	–	–
38	38.000	–	–	–	–	–	–	–	–	0.375	–	–	–	0.500	–	–	–	–	–
40	40.000	–	–	–	–	–	–	–	–	0.375	–	–	–	0.500	–	–	–	–	–
42	42.000	–	–	–	–	–	–	–	–	0.375	–	–	–	0.500	–	–	–	–	–
44	44.000	–	–	–	–	–	–	–	–	0.375	–	–	–	0.500	–	–	–	–	–
46	46.000	–	–	–	–	–	–	–	–	0.375	–	–	–	0.500	–	–	–	–	–
48	48.000	–	–	–	–	–	–	–	–	0.375	–	–	–	0.500	–	–	–	–	–

All values are nominal wall thickness in inches. Inside diameter = OD − 2 × wall. Sch 5 for carbon steel is a light-wall size used mainly with grooved/pressed systems; confirm availability with the mill. Source: Aienginear compilation per ASME B36.10-2022 (welded & seamless wrought steel pipe) and ASME B36.19M (stainless steel pipe). – = no standard wall for that schedule. Verify against the edition named in your project specification.

Complete Pipe Schedule Chart in Millimetres

The same data in SI units, as published in the standards. Use these values for metric isometrics, MTOs and stress models rather than converting inch values yourself.

AIENGINEARPipe Schedule Chart – Wall Thickness in Millimetres (DN 6 to DN 1200)

DN	OD (mm)	5	5S	10	10S	20	30	40	40S	STD	60	80	80S	XS	100	120	140	160	XXS
6	10.3	–	–	1.24	1.24	–	1.45	1.73	1.73	1.73	–	2.41	2.41	2.41	–	–	–	–	–
8	13.7	–	–	1.65	1.65	–	1.85	2.24	2.24	2.24	–	3.02	3.02	3.02	–	–	–	–	–
10	17.1	–	–	1.65	1.65	–	1.85	2.31	2.31	2.31	–	3.20	3.20	3.20	–	–	–	–	–
15	21.3	1.65	1.65	2.11	2.11	–	2.41	2.77	2.77	2.77	–	3.73	3.73	3.73	–	–	–	4.78	7.47
20	26.7	1.65	1.65	2.11	2.11	–	2.41	2.87	2.87	2.87	–	3.91	3.91	3.91	–	–	–	5.56	7.82
25	33.4	1.65	1.65	2.77	2.77	–	2.90	3.38	3.38	3.38	–	4.55	4.55	4.55	–	–	–	6.35	9.09
32	42.2	1.65	1.65	2.77	2.77	–	2.97	3.56	3.56	3.56	–	4.85	4.85	4.85	–	–	–	6.35	9.70
40	48.3	1.65	1.65	2.77	2.77	–	3.18	3.68	3.68	3.68	–	5.08	5.08	5.08	–	–	–	7.14	10.15
50	60.3	1.65	1.65	2.77	2.77	–	3.18	3.91	3.91	3.91	–	5.54	5.54	5.54	–	–	–	8.74	11.07
65	73.0	2.11	2.11	3.05	3.05	–	4.78	5.16	5.16	5.16	–	7.01	7.01	7.01	–	–	–	9.53	14.02
80	88.9	2.11	2.11	3.05	3.05	–	4.78	5.49	5.49	5.49	–	7.62	7.62	7.62	–	–	–	11.13	15.24
90	101.6	2.11	2.11	3.05	3.05	–	4.78	5.74	5.74	5.74	–	8.08	8.08	8.08	–	–	–	–	16.15
100	114.3	2.11	2.11	3.05	3.05	–	4.78	6.02	6.02	6.02	–	8.56	8.56	8.56	–	11.13	–	13.49	17.12
125	141.3	2.77	2.77	3.40	3.40	–	–	6.55	6.55	6.55	–	9.53	9.53	9.53	–	12.70	–	15.88	19.05
150	168.3	2.77	2.77	3.40	3.40	–	–	7.11	7.11	7.11	–	10.97	10.97	10.97	–	14.27	–	18.26	21.95
200	219.1	2.77	2.77	3.76	3.76	6.35	7.04	8.18	8.18	8.18	10.31	12.70	12.70	12.70	15.09	18.26	20.62	23.01	22.23
250	273.0	3.40	3.40	4.19	4.19	6.35	7.80	9.27	9.27	9.27	12.70	15.09	12.70	12.70	18.26	21.44	25.40	28.58	25.40
300	323.8	3.96	3.96	4.57	4.57	6.35	8.38	10.31	9.53	9.53	14.27	17.48	12.70	12.70	21.44	25.40	28.58	33.32	25.40
350	355.6	3.96	3.96	6.35	4.78	7.92	9.53	11.13	9.53	9.53	15.09	19.05	12.70	12.70	23.83	27.79	31.75	35.71	–
400	406.4	4.19	4.19	6.35	4.78	7.92	9.53	12.70	9.53	9.53	16.66	21.44	12.70	12.70	26.19	30.96	36.53	40.49	–
450	457.0	4.19	4.19	6.35	4.78	7.92	11.13	14.27	9.53	9.53	19.05	23.83	12.70	12.70	29.36	34.93	39.67	45.24	–
500	508.0	4.78	4.78	6.35	5.54	9.53	12.70	15.09	9.53	9.53	20.62	26.19	12.70	12.70	32.54	38.10	44.45	50.01	–
550	559.0	4.78	4.78	6.35	5.54	9.53	12.70	–	–	9.53	22.23	28.58	–	12.70	34.93	41.28	47.63	53.98	–
600	610.0	5.54	5.54	6.35	6.35	9.53	14.27	17.48	9.53	9.53	24.61	30.96	12.70	12.70	38.89	46.02	52.37	59.54	–
650	660.0	–	–	7.92	–	12.70	–	–	–	9.53	–	–	–	12.70	–	–	–	–	–
700	711.0	–	–	7.92	–	12.70	15.88	–	–	9.53	–	–	–	12.70	–	–	–	–	–
750	762.0	6.35	6.35	7.92	7.92	12.70	15.88	–	–	9.53	–	–	–	12.70	–	–	–	–	–
800	813.0	–	–	7.92	–	12.70	15.88	17.48	–	9.53	–	–	–	12.70	–	–	–	–	–
850	864.0	–	–	7.92	–	12.70	15.88	17.48	–	9.53	–	–	–	12.70	–	–	–	–	–
900	914.0	–	–	7.92	–	12.70	15.88	19.05	–	9.53	–	–	–	12.70	–	–	–	–	–
950	965.0	–	–	–	–	–	–	–	–	9.53	–	–	–	12.70	–	–	–	–	–
1000	1016.0	–	–	–	–	–	–	–	–	9.53	–	–	–	12.70	–	–	–	–	–
1050	1067.0	–	–	–	–	–	–	–	–	9.53	–	–	–	12.70	–	–	–	–	–
1100	1118.0	–	–	–	–	–	–	–	–	9.53	–	–	–	12.70	–	–	–	–	–
1150	1168.0	–	–	–	–	–	–	–	–	9.53	–	–	–	12.70	–	–	–	–	–
1200	1219.0	–	–	–	–	–	–	–	–	9.53	–	–	–	12.70	–	–	–	–	–

All values are wall thickness in mm; OD in mm. Metric values are the SI figures published in the standards (not simple x25.4 conversions). Inside diameter = OD − 2 × wall. Sch 5 for carbon steel is a light-wall size used mainly with grooved/pressed systems; confirm availability with the mill. Source: Aienginear compilation per ASME B36.10-2022 (welded & seamless wrought steel pipe) and ASME B36.19M (stainless steel pipe). – = no standard wall for that schedule. Verify against the edition named in your project specification.

Carbon Steel Pipe Weight Chart

Weight drives support design, lifting plans and freight. Values below are plain-end steel weight only; add contents, insulation and lining separately (the calculator above adds water for hydrotest load checks).

AIENGINEARCarbon Steel Pipe Weight Chart (lb/ft / kg/m, plain end)

NPS	DN	Sch 40	STD	Sch 80	XS	Sch 160
⅛	6	0.24 / 0.37	0.24 / 0.37	0.31 / 0.47	0.31 / 0.47	–
¼	8	0.43 / 0.63	0.43 / 0.63	0.54 / 0.80	0.54 / 0.80	–
⅜	10	0.57 / 0.84	0.57 / 0.84	0.74 / 1.10	0.74 / 1.10	–
½	15	0.85 / 1.27	0.85 / 1.27	1.09 / 1.62	1.09 / 1.62	1.31 / 1.95
¾	20	1.13 / 1.69	1.13 / 1.69	1.48 / 2.20	1.48 / 2.20	1.95 / 2.90
1	25	1.68 / 2.50	1.68 / 2.50	2.17 / 3.24	2.17 / 3.24	2.85 / 4.24
1¼	32	2.27 / 3.39	2.27 / 3.39	3.00 / 4.47	3.00 / 4.47	3.77 / 5.61
1½	40	2.72 / 4.05	2.72 / 4.05	3.63 / 5.41	3.63 / 5.41	4.86 / 7.25
2	50	3.66 / 5.44	3.66 / 5.44	5.03 / 7.48	5.03 / 7.48	7.47 / 11.11
2½	65	5.80 / 8.63	5.80 / 8.63	7.67 / 11.41	7.67 / 11.41	10.02 / 14.92
3	80	7.58 / 11.29	7.58 / 11.29	10.26 / 15.27	10.26 / 15.27	14.34 / 21.35
3½	90	9.12 / 13.57	9.12 / 13.57	12.52 / 18.64	12.52 / 18.64	–
4	100	10.80 / 16.08	10.80 / 16.08	15.00 / 22.32	15.00 / 22.32	22.53 / 33.54
5	125	14.63 / 21.77	14.63 / 21.77	20.80 / 30.97	20.80 / 30.97	32.99 / 49.12
6	150	18.99 / 28.26	18.99 / 28.26	28.60 / 42.56	28.60 / 42.56	45.39 / 67.57
8	200	28.58 / 42.55	28.58 / 42.55	43.43 / 64.64	43.43 / 64.64	74.76 / 111.27
10	250	40.52 / 60.29	40.52 / 60.29	64.49 / 95.98	54.79 / 81.53	115.75 / 172.27
12	300	53.57 / 79.71	49.61 / 73.86	88.71 / 132.05	65.48 / 97.44	160.42 / 238.69
14	350	63.50 / 94.55	54.62 / 81.33	106.23 / 158.11	72.16 / 107.40	189.29 / 281.72
16	400	82.85 / 123.31	62.64 / 93.27	136.74 / 203.54	82.85 / 123.31	245.48 / 365.38
18	450	104.76 / 155.81	70.65 / 105.17	171.08 / 254.57	93.54 / 139.16	308.79 / 459.39
20	500	123.23 / 183.43	78.67 / 117.15	209.06 / 311.19	104.23 / 155.13	379.53 / 564.85
22	550	–	86.69 / 129.14	251.05 / 373.85	114.92 / 171.10	451.49 / 672.30
24	600	171.45 / 255.43	94.71 / 141.12	296.86 / 442.11	125.61 / 187.07	542.64 / 808.27
26	650	–	102.72 / 152.88	–	136.30 / 202.74	–
28	700	–	110.74 / 164.86	–	146.99 / 218.71	–
30	750	–	118.76 / 176.85	–	157.68 / 234.68	–
32	800	230.29 / 342.94	126.78 / 188.83	–	168.37 / 250.65	–
34	850	245.00 / 364.92	134.79 / 200.82	–	179.06 / 266.63	–
36	900	282.62 / 420.45	142.81 / 212.57	–	189.75 / 282.29	–
38	950	–	150.83 / 224.56	–	200.44 / 298.26	–
40	1000	–	158.85 / 236.54	–	211.13 / 314.23	–
42	1050	–	166.86 / 248.53	–	221.82 / 330.21	–
44	1100	–	174.88 / 260.52	–	232.51 / 346.18	–
46	1150	–	182.90 / 272.27	–	243.20 / 361.84	–
48	1200	–	190.92 / 284.25	–	253.89 / 377.81	–

Calculated with the ASME B36.10 plain-end mass equations: W = 10.69 (D − t) t [lb/ft, inches] and W = 0.0246615 (D − t) t [kg/m, mm], for carbon steel (7.85 g/cm³). Austenitic stainless steel is about 2% heavier. Results may differ from tabulated values in the last digit.

Pipe Dimensional Tolerances (ASTM A530)

Nominal dimensions are never exact. ASTM A530/A530M sets general permissible variations for many seamless and welded steel pipe specifications. The most important number for designers is the −12.5% under-tolerance on wall, which is why piping codes require the nominal wall to satisfy t_nominal × 0.875 ≥ t_required.

AIENGINEARPermissible Variations – ASTM A530/A530M

Characteristic	Size range	Over (+)	Under (−)
Weight (mass)	NPS 12 (DN 300) and smaller	+10%	−3.5%
Weight (mass)	Larger than NPS 12	+10%	−5%
Wall – seamless & welded	NPS ⅛ to 2½, all t/D	+20.0%	−12.5%
Wall – seamless & welded	NPS 3 to 18, t/D ≤ 5%	+22.5%	−12.5%
Wall – seamless & welded	NPS 3 to 18, t/D > 5%	+15.0%	−12.5%
Wall – welded	NPS 20 and larger, all t/D	+17.5%	−12.5%
Wall – seamless	NPS 20 and larger, t/D ≤ 5%	+22.5%	−12.5%
Wall – seamless	NPS 20 and larger, t/D > 5%	+15.0%	−12.5%
Wall – forged & bored	All sizes	+⅛ in (3.2 mm)	0
Wall – cast	All sizes	+1/16 in (1.6 mm)	0
ID – cast pipe	All sizes	0	−1/16 in (1.6 mm)
Outside diameter	NPS ⅛ to 1½	+1/64 in (0.4 mm)	−1/32 in (0.8 mm)
Outside diameter	Over 1½ to 4	+1/32 in (0.8 mm)	−1/32 in (0.8 mm)
Outside diameter	Over 4 to 8	+1/16 in (1.6 mm)	−1/32 in (0.8 mm)
Outside diameter	Over 8 to 18	+3/32 in (2.4 mm)	−1/32 in (0.8 mm)
Outside diameter	Over 18 to 26	+⅛ in (3.2 mm)	−1/32 in (0.8 mm)
Outside diameter	Over 26 to 34	+5/32 in (4.0 mm)	−1/32 in (0.8 mm)
Outside diameter	Over 34 to 48	+3/16 in (4.8 mm)	−1/32 in (0.8 mm)

t/D = nominal wall / specified OD. For welded pipe the weld-bead reinforcement is not counted in wall tolerance. Weight tolerance applies to pipe ordered to nominal wall. The product specification (e.g. ASTM A106, A333, A335, A312) overrides A530 where it states its own limits – ASTM A53, for example, is not covered by A530 and sets its own tolerances.

How to Select the Right Schedule (Engineering Method)

The schedule is the output of a design calculation, not a starting assumption. For process piping under ASME B31.3 (para. 304.1.2), the straight-pipe procedure is:

Pressure design thickness: t = P D / [2 (S E W + P Y)] – P design pressure, D OD, S allowable stress at design temperature, E quality factor, W weld joint strength reduction factor, Y coefficient (0.4 for ferritic steel below 900 °F).
Add allowances: t_m = t + c, where c = corrosion/erosion allowance + thread or groove depth.
Allow for mill tolerance: t_nominal ≥ t_m / 0.875.
Pick the next schedule up from the chart and confirm it also meets mechanical, branch-reinforcement and support needs.

Worked example (illustrative)

NPS 6 seamless ASTM A106 Gr. B, P = 1000 psig at 100 °F, S = 20,000 psi, E = 1.0, W = 1.0, Y = 0.4, c = 1/16 in.
t = 1000 × 6.625 / [2 (20,000 + 400)] = 0.162 in → t_m = 0.162 + 0.0625 = 0.225 in → t_nominal ≥ 0.225 / 0.875 = 0.257 in.
Sch 40 (0.280 in) is the lightest standard wall that passes. Always confirm S, E, W and Y from the code edition and material table that apply to your project.

How to Specify Pipe on a Datasheet or BOM

From years of site construction and shutdown work, most pipe supply problems start with an incomplete description. A complete line item reads like this:

PIPE, NPS 6 (DN 150), SCH 40 (7.11 mm), SMLS, BE, ASTM A106 Gr. B, ASME B36.10, 6 m random length

Common mistakes to avoid

Writing only "6 inch pipe" – no wall, no standard, no material.
Using "Sch 40" for stainless pipe NPS 12+ when Sch 40S was intended (or vice versa).
Assuming DN 65 or DN 125 European pipe will fit ASME fittings.
Treating Sch 80 as a pressure rating without a code calculation at design temperature.
Forgetting that STD and Sch 40 differ above NPS 10.
Ignoring the −12.5% mill tolerance when checking corroded wall during inspection.

Key Facts – Printable Summary

AIENGINEARPipe Size & Schedule – Key Facts

Term	Meaning	Engineering note
NPS	Nominal Pipe Size (inch-based designator)	Not the actual ID or OD below NPS 14
DN	Diamètre Nominal (metric designator, ISO 6708)	Dimensionless – DN 50 is not 50 mm of anything
OD	Outside diameter	Fixed for each NPS; does not change with schedule
ID	Inside diameter = OD − 2t	Falls as schedule rises
Schedule	Wall-thickness designation	Not a pressure rating by itself
STD / XS / XXS	Legacy weight classes	STD = Sch 40 to NPS 10; XS = Sch 80 to NPS 8
S-schedules	5S, 10S, 40S, 80S (ASME B36.19M)	Differ from 10/40/80 for NPS 10+ (see table)
Mill tolerance	Typically −12.5% on wall	Minimum wall = 0.875 × nominal
Weight formula	W = 10.69 (D − t) t	lb/ft, D and t in inches, carbon steel

Quick-reference summary by Aienginear. Print it and keep it with your piping specification.

Frequently Asked Questions

What is a pipe schedule?

A pipe schedule is a standard designation of wall thickness (Sch 5 to Sch 160, plus STD, XS and XXS). For the same NPS, a higher schedule means a thicker wall and smaller inside diameter, while the OD stays the same.

What is the difference between NPS and DN?

NPS is the inch-based North American designator; DN is the dimensionless metric designator from ISO 6708. They refer to the same pipe – NPS 2 = DN 50 – and neither is the actual inside or outside diameter.

Is DN 50 pipe 50 mm inside diameter?

No. DN 50 has an OD of 60.3 mm. Its ID is 52.5 mm in Sch 40 and 49.2 mm in Sch 80.

How do you calculate pipe inside diameter?

ID = OD − 2 × wall thickness. For NPS 2 Sch 40: 2.375 − 2 × 0.154 = 2.067 in (52.5 mm).

What is the OD of a 2 inch pipe?

2.375 in (60.3 mm), for every schedule.

Is Schedule 80 stronger than Schedule 40?

For the same NPS and material, Sch 80 has a thicker wall and therefore a higher pressure capacity. The allowable pressure must still be calculated to the governing code (ASME B31.3, B31.1 etc.) at design temperature, including corrosion allowance and mill tolerance.

What is the difference between Schedule 40 and 40S?

Sch 40 comes from ASME B36.10 (carbon steel); 40S from ASME B36.19M (stainless). They are identical up to NPS 10. From NPS 12 upward 40S is thinner – for example NPS 12 Sch 40 is 0.406 in while 40S is 0.375 in.

Is STD the same as Schedule 40?

Only from NPS ⅛ to NPS 10. From NPS 12 upward STD stays 0.375 in (9.53 mm) while Sch 40 becomes thicker; NPS 22 has no Sch 40 at all.

What does NB mean in pipe size?

NB (Nominal Bore) is an informal term equivalent to NPS. In specifications, write NPS or DN plus schedule or wall thickness to avoid ambiguity.

Which standards define pipe sizes and schedules?

ASME B36.10 (wrought steel pipe), ASME B36.19M (stainless steel pipe), ISO 6708 (DN) and, in Europe, EN 10220 / ISO 4200. Tolerances come from ASTM A530 or the individual product specification.

What is the mill tolerance on pipe wall thickness?

Most seamless and welded pipe specifications allow the wall to be up to 12.5% under nominal at any point, so design uses 87.5% of the nominal wall.

How much does NPS 6 Sch 40 pipe weigh?

About 18.99 lb/ft (28.26 kg/m) for carbon steel, plain end.

Free Printable Pipe Size Charts

Every table on this page has a Print / PDF button that produces a branded A4 sheet. You can also download the ready-made pocket charts:

Pipe Schedule Chart – Inches (PDF) Pipe Schedule Chart – mm (PDF) NPS / DN / OD Chart (PDF)

Pipe Sizes & Schedules Quiz

References

ASME B36.10-2022, Welded and Seamless Wrought Steel Pipe, The American Society of Mechanical Engineers.
ASME B36.19M-2018, Stainless Steel Pipe, ASME.
ASTM A530/A530M, General Requirements for Specialized Carbon and Alloy Steel Pipe, ASTM International (current edition).
ASME B31.3, Process Piping, para. 304.1.2 – Straight pipe under internal pressure.
ISO 6708, Pipework components – Definition and selection of DN; EN 10220, Seamless and welded steel tubes – Dimensions and masses per unit length.

Reviewed by Muhammad Raza, Founder of Aienginear and Head of Projects in power, cement, fertilizer and oil & gas construction. Last technical review: 11 October 2026. Data compiled and cross-checked by Aienginear; tables are for reference – the edition of each standard named in your project specification governs. Found an error? Tell us.

Written by Muhammad Raza

Founder of Aienginear. Engineering and digital solutions professional with 26+ years managing projects, plant shutdowns and turnarounds in oil & gas, petrochemical and power generation.

LinkedIn · YouTube · Report an error or ask a question

Pipe Sizes and Pipe Schedule Chart (NPS, DN, OD, ID & Wall Thickness)