Choose a task to calculate BSFC, fuel mass flow, brake shaft power, thermal efficiency or unit conversions. Efficiency requires the actual fuel’s lower heating value; optional volume flow requires its density.

Use fuel mass flow and brake (shaft) power at the same operating point. BSFC is mass per output energy, not a percentage.

BSFC Formula

The following formula is used to calculate brake-specific fuel consumption.

BSFC = 3,600,000 × r / P
  • Where BSFC is the brake-specific fuel consumption (g/kWh)
  • r is the standard rate of fuel consumption (grams per second, g/s)
  • P is the power output by the engine (watts, W)

To calculate brake specific fuel consumption (BSFC), divide fuel flow in g/s by brake shaft power in W, then multiply by 3,600,000 to express the result in g/kWh.

BSFC Definition

What is BSFC?

BSFC, which is short for brake-specific fuel consumption, is a measure of the fuel efficiency of any engine that burns fuel in order to produce a rotational movement and power.

Example Problem

How to calculate BSFC?

  1. First, determine the rate of fuel consumption of the engine.

    In this example, the engine consumes a total of 2.75 grams of fuel per second.

  2. Next, determine the power output of the engine.

    This engine is able to output 40,000 watts of shaft power.

  3. Finally, calculate the BSFC.

    Using the formula, the brake-specific fuel consumption is found to be:
    BSFC = 3,600,000 × r / P
    BSFC = 3,600,000 × 2.75/40,000
    BSFC = 3,600,000 × r / P
    BSFC = 247.5 g/kWh