Understanding Fuel Injector Flow Ratings
Fuel injectors are rated by flow capacity in two competing units: lb/hr (pounds per hour, mass-based) is the standard in the United States and across most domestic automotive performance catalogs, while cc/min (cubic centimeters per minute, volume-based) dominates the import scene, Japanese OEM parts catalogs and most European data sheets. Converting between them is not a single fixed ratio — it depends on fuel density, expressed as specific gravity (SG). Pump gasoline has an SG around 0.74. E85 sits near 0.78. Methanol is denser still at roughly 0.79, and diesel checks in at 0.83. Every fuel needs its own conversion ratio, which is why a single "divide by 10.5" rule only really works on gasoline.
This calculator handles every common fuel and lets you enter a custom SG for race blends or oxygenated specialty fuels. It also corrects for temperature — fuel density drops as it heats up, by roughly 0.0007 SG units per degree Celsius. If you're doing dyno work in a 100°F engine bay or tuning at altitude, the difference adds up. Beyond raw conversion, the calculator translates flow rates into the language tuners actually think in: supported horsepower at common cylinder counts, the closest standard injector size you can actually order, and equivalent mass flow in g/s for OEM datasheet cross-references. Whether you're swapping your factory ECU for a standalone, going E85 on a turbocharged build, or sizing injectors for a methanol drag car, this is the conversion tool you reach for first.