Work out gas flow rate instantly with clear inputs, formula shown and shareable results.
Gas flow is simply input rating divided by heating value. The clocking time is the practical field check: with all other appliances off, timing one cubic foot on the meter dial should match 3600 divided by the calculated flow, which confirms the appliance is firing at its nameplate rate.
Gas flow
ft³/h = input BTU/h / heating value BTU/ft³
Meter clocking
seconds per ft³ = 3600 / (ft³/h)
ft³/h = input BTU/h / heating value BTU/ft³. Gas flow is simply input rating divided by heating value.
The appliance is overfiring, usually from high manifold pressure or a wrong orifice. Both waste fuel and can produce carbon monoxide.
This calculator takes 2 inputs: Appliance input rating, Gas heating value. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.