Orifice Plate Flow Calculator

Aienginear · ISO 5167-1 / ISO 5167-2:2022 · v2.0.0Self-test…

1. What do you want to calculate?

Fluid phase

Fluid preset (optional)

Pressure tappings

Tag / item no.

2. Pipe and orifice plate

Pipe NPS (ASME B36.10M)

Schedule

Pipe material

Pipe internal diameter D at 20 °C

From pipe table; overwrite with measured ID for best accuracy.

Orifice bore d at 20 °C

Plate material

Differential pressure Δp

Flow rate (design / maximum)

3. Fluid at upstream tapping

Upstream pressure p₁ (absolute)

Temperature T₁

Gas density method

Molar mass M (kg/kmol)

Compressibility Z at p₁, T₁

Density ρ₁

Dynamic viscosity μ

Isentropic exponent κ

Vapour pressure p_v (optional)

Z at standard conditions

4. Plate geometry, roughness & transmitter (optional)

Plate thickness E

Bore edge thickness e

Pipe roughness Ra

DP transmitter upper range value (URV)

Transmitter accuracy (% of span, k=2)

Minimum operating flow (optional, same unit as flow)

Leave optional fields blank to skip their checks. Nothing is assumed silently.

Results update automatically as you type.

Mass flow rate

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Enter the inputs to calculate.

Results

ISO 5167-2 limits summary

Validity checks (ISO 5167-1 / ISO 5167-2:2022)

Upstream and downstream straight lengths

Upstream fitting nearest the plate

Design basis

Available upstream length (in D, optional)

Summary based on ISO 5167-2 Table 3 (values in pipe diameters D, upstream length measured from the upstream face of the plate). For a β between rows the value of the next higher β row is used. ISO 5167-2:2022 corrected the two-45°-bend spacing and clarified the tee configuration; always confirm against your licensed copy, and consider a flow conditioner (Annex C) where space is short.

Input uncertainties (relative expanded, k = 2)

Pipe ID D (%)

Bore d (%)

Density ρ₁ (%)

Δp uncertainty comes from transmitter accuracy × URV / Δp (tab 4 of the calculator). C and ε uncertainties are taken from ISO 5167-2 clause 5.3.3.

Uncertainty budget for qₘ (ISO 5167-1 / GUM)

Flow vs differential pressure (square-root law)

Transmitter scaling table

Use this table to configure square-root extraction in the transmitter or DCS. Readings below about 10 % of DP span (about 32 % of flow) carry much larger uncertainty; consider stacked transmitters or a smart wide-range transmitter for high turndown.

Running cost of the permanent pressure loss

Operating hours per year

Pump / compressor + driver efficiency (%)

Energy tariff per kWh

Currency

Hydraulic power lost = actual volume flow × permanent pressure loss ÷ efficiency. For a compressible fluid this is a screening estimate based on upstream density.

Runtime self-test (publication gate)

Expected values were derived independently of this page (separate reference implementation of ISO 5167-2 equations, unit definitions from NIST SP 811 and ASME B36.10M dimensions). The badge in the header turns green only when every test passes.

Engineering disclaimer. This is a preliminary engineering / design-support calculator based on the equations of ISO 5167-1 and ISO 5167-2:2022. It does not replace the standard, a licensed copy of it, vendor sizing software or qualified engineering review. Custody-transfer, fiscal and safety-related measurement requires full compliance with the applicable standard, contract and local regulations. © 2026 Aienginear.com · Muhammad Raza · Report an issue