Work out gas pipe sizing instantly with clear inputs, formula shown and shareable results.
Low-pressure fuel gas piping is sized by the longest-length method. Connected load divided by heating value gives the cubic feet per hour to deliver, and the low-pressure flow equation Q = 2313 D^2.623 (Δp / (Cr L))^0.541 is inverted to find the bore, with Cr = 0.6094 for natural gas at 0.60 specific gravity.
Gas flow capacity
Q = 2313 x D^2.623 x (Δp / (Cr x L))^0.541
Required flow
ft³/h = connected load BTU/h / heating value BTU/ft³
Preliminary estimate only. Fuel gas piping must be sized and installed by a licensed professional to the applicable fuel gas code.
Q = 2313 x D^2.623 x (Δp / (Cr x L))^0.541. Low-pressure fuel gas piping is sized by the longest-length method.
The longest-length method already carries an allowance for normal fittings. Unusual arrangements with many elbows or a long flexible connector should be checked by the equivalent length method instead.
This calculator takes 4 inputs: Connected gas load, Gas heating value, Longest run length, Allowable pressure drop. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.