BSFC Calculator
Convert brake specific fuel consumption and horsepower into the fuel flow you need in pounds, gallons, and liters per hour.
How to Use This Calculator
Enter engine horsepower
Use crank horsepower for injector sizing or wheel horsepower for chassis dyno comparisons.
Input the BSFC value
Typical gasoline engines range 0.45–0.60 lb/hp·hr, while forced-induction builds can be 0.55–0.75.
Adjust fuel density
Gasoline ≈ 6.17 lb/gal, E85 ≈ 6.6 lb/gal, Diesel ≈ 7.1 lb/gal.
Review the fuel flow results
Compare to injector capacity or pump volume to ensure the fuel system can keep up.
Formula
Fuel Flow (lb/hr) = Horsepower × BSFC
Gallons per hour: GPH = (HP × BSFC) ÷ Fuel Density
Liters per hour: LPH = GPH × 3.78541
Example with 300 hp, 0.50 lb/hp·hr, and gasoline at 6.17 lb/gal:
Fuel (lb/hr) = 300 × 0.50 = 150 lb/hr
GPH = 150 ÷ 6.17 = 24.3 gph → LPH = 24.3 × 3.78541 = 92.0 L/h
About the BSFC Calculator
Brake specific fuel consumption (BSFC) expresses how efficiently an engine converts fuel mass into horsepower. Lower numbers indicate better efficiency. This calculator turns that efficiency figure into actual fuel flow values so you can size injectors, pumps, and fuel lines.
When to Use This Calculator
- Fuel system design: Ensure injectors, pumps, and regulators can support target horsepower.
- Dyno tuning: Cross-check measured BSFC numbers from engine dynos.
- Race preparation: Estimate fuel consumption for endurance events to plan refueling.
- Propulsion studies: Compare efficiency between gasoline, ethanol, and diesel setups.
Why Use Our Calculator?
- ✅ Multiple outputs: Instantly view fuel demand in pounds, gallons, and liters per hour.
- ✅ Flexible density: Model any fuel blend by adjusting the density value.
- ✅ Quick validation: Double-check that a proposed build stays within fuel system capacity.
- ✅ Track-friendly: Works on mobile devices for real-time tuning sessions.
Common Applications
Injector sizing: Convert required lb/hr into injector cc/min by combining with duty-cycle calculators.
Aviation and marine engines: Plan flight or voyage fuel loads based on expected power settings.
Hybrid setups: Estimate fuel demand for range extenders or auxiliary power units.
Tips for Best Results
- Use BSFC data from the same fuel type you plan to run.
- Increase the BSFC value for rich mixtures or forced induction safety margins.
- Compare the resulting flow to pump and injector capacity with appropriate duty cycle limits.
- Recalculate whenever horsepower goals change during the build.
Frequently Asked Questions
What is a good BSFC number?
Naturally aspirated gasoline engines typically achieve 0.45–0.55 lb/hp·hr. Lower numbers are more efficient. Forced induction often pushes BSFC to 0.55–0.70 to maintain safe air-fuel ratios.
Can I use metric units?
Enter horsepower in hp and BSFC in lb/hp·hr, then read the result in liters per hour. You can convert horsepower from kilowatts by multiplying by 1.341.
How do I find the right fuel density?
Fuel suppliers publish density at 60°F. Gasoline averages 6.17 lb/gal, E85 around 6.6, and diesel about 7.1. Adjust for temperature if precision is critical.
Does injector duty cycle matter?
Yes. After calculating required fuel flow, divide by the number of injectors and factor in desired duty cycle (usually 80%) to ensure each injector can deliver the needed flow.