BSFC Calculator (Brake Specific Fuel Consumption)

Enter your engine's fuel consumption rate and power output to calculate Brake Specific Fuel Consumption (BSFC) — the key metric for engine efficiency. You can provide torque and RPM instead of power output, and optionally select a fuel type to get thermal efficiency as well. Results are shown in both metric (g/kWh) and imperial (lb/hp·hr) units. Also try the calculate 0-60 mph Time, 0-100 kph Time & Quarter Mile Time — 0-60.

Unit System *

Select fuel type to auto-fill energy density and calculate thermal efficiency

MJ/kg

Auto-filled based on fuel type; override for custom fuels

g/s

Mass flow rate of fuel consumed by the engine

kW

Brake power at the crankshaft. Or calculate from torque & RPM below.

N·m

Used to compute power if Power Output is not provided

RPM

Used with torque to compute power if Power Output is not provided

Results

BSFC (Metric)

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BSFC (Imperial)

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Engine Power Used

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Thermal Efficiency

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Fuel Flow Rate

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What is Brake Specific Fuel Consumption (BSFC)?

BSFC is a measure of the fuel efficiency of an internal combustion engine that produces rotational (shaft) power. It is calculated as the ratio of the fuel mass flow rate to the engine's brake power output. A lower BSFC value indicates a more efficient engine. See also our RPM Calculator.

How do I calculate BSFC?

BSFC = Fuel Mass Flow Rate / Engine Power Output. In metric units: divide fuel flow in grams per second by power in kilowatts, then multiply by 3600 to convert to g/kWh. For example, an engine consuming 14.78 g/s and producing 250 kW has a BSFC of (14.78 / 250) × 3600 = 212.6 g/kWh.

What is the brake-specific fuel consumption?

It is a performance metric specific to engines that convert chemical energy in fuel into mechanical (rotational) energy. The 'brake' in the name refers to the use of a dynamometer (an electrical brake) used to measure torque and power during engine testing.

Is a lower BSFC good?

Yes — a lower BSFC means the engine is consuming less fuel per unit of power produced, indicating higher efficiency. Diesel engines typically achieve BSFC values of 200–300 g/kWh, while gasoline engines range from 250–350 g/kWh. Highly optimized diesel engines can reach as low as 170 g/kWh. You might also find our calculate Your Miles Are Worth, Effective Cents Per Mile (Award) & Total Cost of Award Flight — Miles to Dollars useful.

How do I calculate power from torque and RPM?

Engine power can be computed from torque and rotational speed using: Power (kW) = Torque (N·m) × RPM × 2π / 60,000. This calculator accepts torque and RPM as optional inputs and automatically computes power if the direct power output field is left at zero.

How is BSFC used to calculate engine efficiency?

Thermal efficiency = 3,600,000 / (BSFC × Energy Density of Fuel). The energy density is in kJ/kg and BSFC in g/kWh. For instance, a gasoline engine (energy density ~44,400 kJ/kg) with a BSFC of 212.6 g/kWh has a thermal efficiency of about 38%.

What are typical BSFC values for different engine types?

Gasoline engines: 250–350 g/kWh (0.40–0.57 lb/hp·hr). Diesel engines: 200–300 g/kWh (0.33–0.49 lb/hp·hr). Turbocharged diesel engines: 170–220 g/kWh (0.28–0.36 lb/hp·hr). The lowest BSFC typically occurs at mid-to-high load operating points.

Can BSFC be used for any engine type?

BSFC applies to any internal combustion engine that produces shaft (rotational) power, including gasoline, diesel, LPG, and natural gas engines. It is widely used in automotive, marine, and industrial engine performance analysis and tuning.