BSFC Calculator — Brake-Specific Fuel Consumption
Enter fuel mass flow rate and brake power (or torque + RPM) to calculate Brake-Specific Fuel Consumption — the standard metric for comparing fuel efficiency across engines of any size or type, independent of displacement.
Specify brake power via
kg/h
kW
Brake-specific fuel consumption — fuel mass per unit of work output
- 1
Fuel flow in g/h
15 × 1,000 = 15,000Convert fuel mass flow from kg/h to g/h for the BSFC formula. - 2
BSFC
15,000 ÷ 60 = 250
How does this calculator work?
BSFC (g/kW·h) = fuel mass flow (g/h) ÷ brake power (kW). It measures fuel consumed per unit of useful work — lower is more efficient. Good diesel: 185–250 g/kW·h; typical gasoline: 260–330 g/kW·h. Thermal efficiency ≈ 3 600 ÷ (BSFC_kg × LHV_kJ/kg).
Formula
How this is calculated
Brake-Specific Fuel Consumption (BSFC) measures how much fuel mass an engine burns to produce one unit of useful shaft work — specifically, grams of fuel per kilowatt-hour of output. Because it normalises by power output rather than displacement or cylinder count, it is the standard industry metric for comparing the fuel efficiency of different engines, operating points, and fuel types.
BSFC is measured on an engine dynamometer at a specific speed and load point. The same engine has different BSFC at different operating conditions: most engines reach their best-efficiency island (lowest BSFC) at moderate load and moderate RPM, which is why hybrid vehicles use engine-on strategies that keep the combustion engine near its BSFC sweet spot.
Typical reference values (approximate, 2020s technology): large two-stroke marine diesel engines achieve 155–185 g/kW·h; modern common-rail diesel cars 200–250 g/kW·h; naturally aspirated gasoline cars 250–330 g/kW·h at peak-efficiency load; small gasoline engines above 400 g/kW·h at light load. The thermal efficiency estimate in the output uses a gasoline lower heating value of 44 MJ/kg — substitute your actual fuel LHV for diesel, ethanol, or other fuels.
Frequently asked questions
The lower the BSFC, the more efficient the engine. Modern diesel passenger-car engines achieve 200–250 g/kW·h at their best operating point. Naturally aspirated gasoline engines typically range 260–330 g/kW·h. The best large two-stroke marine diesel engines reach below 160 g/kW·h — approaching the thermodynamic limit. Values above 400 g/kW·h are generally poor (light-load operation or old technology).
Thermal efficiency η = 3 600 / (BSFC_kg × LHV), where BSFC is in kg/kW·h and LHV is the fuel's lower heating value in kJ/kg. A BSFC of 200 g/kW·h with diesel (LHV ≈ 43 MJ/kg) gives η ≈ 42 %. A BSFC of 250 g/kW·h with gasoline (LHV ≈ 44 MJ/kg) gives η ≈ 33 %.
No — BSFC varies significantly across the engine's operating map. Most engines have a sweet spot (lowest BSFC "island") at 60–80 % of peak load and moderate RPM. At idle or very light load, combustion efficiency drops and BSFC rises steeply. At peak power, enrichment or valve timing compromises also raise BSFC. Always specify the operating point when reporting a BSFC figure.
Also known as
TG we-Calculate Editorial Team. (2026). BSFC Calculator — Brake-Specific Fuel Consumption [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/brake-specific-fuel-consumption-calculator
TG we-Calculate Editorial Team. "BSFC Calculator — Brake-Specific Fuel Consumption." TG we-Calculate. 2026. https://we-calculate.com/calculator/brake-specific-fuel-consumption-calculator.
TG we-Calculate Editorial Team, "BSFC Calculator — Brake-Specific Fuel Consumption," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/brake-specific-fuel-consumption-calculator
@misc{wecalculate_brake_specific_fuel_consumption_calculator, title = {BSFC Calculator — Brake-Specific Fuel Consumption}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/brake-specific-fuel-consumption-calculator}}, year = {2026}, note = {TG we-Calculate} }
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