OrificeGpm · fluids
OrificeGpm orifice flow gpm
Screen orifice flow before selecting a plate or nozzle for a gravity-head tank outlet
Result
A_ft2=π(d_in/12/2)²; Q_cfs=Cd·A·√(2·g·head) with g=32.174; gpm=Q_cfs·448.831
How to use this estimate
Estimate orifice discharge in GPM from Cd, orifice diameter, and head using the orifice equation. How it works: A_ft2=π(d_in/12/2)²; Q_cfs=Cd·A·√(2·g·head) with g=32.174; gpm=Q_cfs·448.831. Out of scope: compressibility; cavitation; ISO orifice meter expansions; pump curves. This is an approximate screening estimate, not a substitute for manufacturer charts or a full engineering design. Does not certify code compliance; confirm manufacturer data where it applies.
Sources, methodology, and assumptions
Methodology
A_ft2=π(d_in/12/2)²; Q_cfs=Cd·A·√(2·g·head) with g=32.174; gpm=Q_cfs·448.831
Assumptions
Incompressible liquid; User Cd; g=32.174 ft/s². This is an approximate screening estimate, not a substitute for manufacturer charts or a full engineering design.
Out of scope
compressibility; cavitation; ISO orifice meter expansions; pump curves
Sources
Last technically reviewed: 2026-09-11