How to Use BSFC Calculator
The BSFC Calculator turns a fuel-flow and a power reading into a brake-specific fuel consumption number — the most common metric for comparing engine efficiency across cylinders, displacements and fuels.
- Select fuel type — Gasoline or diesel. The BSFC Calculator uses fuel density for volumetric units.
- Enter fuel flow — Pick the unit you measured in: g/h, kg/h, lb/h, L/h, or gal/h.
- Enter brake power — In kW or hp, taken from the dyno or ECU log.
- Read the result panel — BSFC in g/kWh and lb/hp·hr, estimated thermal efficiency, plus a power-unit cross-check.
Formula & Theory - BSFC Calculator
The BSFC Calculator uses the standard equation:
BSFC (g/kWh) = fuel_flow_g_per_hr / power_kW
BSFC (lb/hp·hr) = BSFC_g_per_kWh / 608.277
η_thermal ≈ 3 600 000 / (BSFC × LHV_fuel_J_per_g)| Symbol | Meaning |
|---|---|
| fuel_flow_g_per_hr | Fuel flow converted to grams per hour |
| power_kW | Brake power in kilowatts |
| LHV_fuel | Lower heating value of the fuel |
| η_thermal | Theoretical thermal efficiency |
Assumptions and Limits
The BSFC Calculator assumes a single, steady operating point. Real engines have a BSFC map that varies with rpm and load. Thermal efficiency assumes gasoline LHV (43 MJ/kg) or diesel LHV (~42.7 MJ/kg).
Use Cases for BSFC Calculator
- Engine benchmarking — Compare engines on equal footing regardless of displacement.
- Tune validation — Verify that a new map improved efficiency, not just power.
- Research projects — Reduce dyno spreadsheets to a single comparable number.
- Marine and aviation — Reciprocating engines often quote BSFC directly.
- Vehicle reviews — Cross-check published efficiency claims.
Use the BSFC Calculator any time you want to translate raw fuel-flow data into a directly comparable efficiency figure.