How the conversion works
cc/min is a volume: cubic centimeters per minute, read straight off the flow bench. lb/hr is a weight: pounds per hour, the unit your tuner and your ECU calibration think in. Both describe the same flow rate, the way miles per hour and kilometers per hour describe the same speed. To move between them you need one thing the bench does not measure directly: the fuel's density, written as specific gravity.
lb/hr = cc/min × 60 × specific gravity ÷ 453.592
For pump gasoline at a specific gravity of 0.72, that simplifies to 1 lb/hr ≈ 10.5 cc/min.
Run E85 and the multiplier shifts, because ethanol is denser than gasoline: specific gravity climbs to about 0.785, so the same injector reads a higher lb/hr number. Methanol is denser still. The formula never changes, only the specific gravity does. That is why this calculator lets you pick the fuel or type in your own number.
A word on precision. Injector makers rate flow at a test pressure, usually 3 bar, about 43.5 psi, and published specific gravities vary a little by blend and temperature. Treat the result as a close working figure, not a lab certificate. If you want the real delivery on your actual injectors, that is what the bench measures, before and after cleaning.
Want the longer version of why these numbers matter for your engine? Read why flow testing matters, or check the injector types guide to identify what's in your outboard or auto.