Inputs

This is a basic incompressible liquid orifice calculation using a user-supplied discharge coefficient. A default Cd of 0.61 is only a starting estimate, not a universal value. Metering-standard calculations can require a Reynolds-dependent Cd, tap geometry, expansibility, and other corrections.

Solve for

Discharge coefficient, Cd

Pipe inside diameter

Pipe diameter unit

Orifice bore diameter

Orifice diameter unit

Liquid density

Density unit

Differential pressure

Pressure unit

Results

Flow rate

—

Differential pressure

—

Beta ratio, d/D

—

Orifice area

—

Equation

Q = Cd Aₒ √[ 2ΔP / (ρ(1 − β⁴)) ]
β = d/D

The equation includes the velocity-of-approach correction for an orifice in a larger pipe. It assumes an incompressible liquid and a supplied discharge coefficient. Do not use this simple form for gas/steam flow or as a substitute for a required metering standard.