Engineering calculator reviewed for preliminary design use · Last updated: March 2026
Calculate orifice plate flow measurement per ISO 5167. Compute volumetric and mass flow rates from differential pressure, discharge coefficient Cd, fluid density, and orifice diameter. Apply to differential pressure flowmeter design and calibration.
Orifice Flow Calculation
An orifice plate flowmeter uses a restriction inserted in the pipe to create a differential pressure proportional to the flow rate squared. It is one of the most widely used flow measurement devices in oil, gas, and chemical plants due to its simplicity and reliability.
The discharge coefficient depends on the beta ratio (d/D) and Reynolds number. A value of 0.61 is commonly used for initial sizing. Calibrated values should be used for custody transfer applications.
Applications
Process flow measurement and control
Steam, gas, and liquid metering
Combined with differential pressure transmitters for flow monitoring
Cd accounts for the vena contracta effect — the actual flow area is smaller than the orifice bore. Typical Cd values range from 0.60 to 0.65 for sharp-edge orifice plates. It depends on beta ratio and Reynolds number.
Is this accurate for gas flow measurement?
For gas flow, an expansion factor Y must be applied. This calculator provides liquid flow calculation. For gas, use ISO 5167 Part 2 with appropriate expansion factor correction.
These results are preliminary estimates for screening-level design use. They do not replace detailed engineering, code compliance verification, or vendor-certified calculations.