Engine Thermal Efficiency from BSFC Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 26, 2026Engine Thermal Efficiency from BSFC Calculator
Brake specific fuel consumption is usually reported as a standalone number, but it converts directly into thermal efficiency once you know the fuel's heating value - arguably a more intuitive way to understand how "efficient" an engine actually is.
The Formula
Efficiency % = 3600 / (BSFC × LHV) × 100
Worked Example
A BSFC of 250 g/kWh with a fuel LHV of 43 MJ/kg: Efficiency = 3600 / (250 × 43) × 100 ≈ 33.5%
How to Use This Calculator
- Enter brake specific fuel consumption in g/kWh.
- Enter the fuel's lower heating value in MJ/kg.
Lower BSFC always corresponds to higher thermal efficiency for a given fuel - the two numbers describe the exact same underlying performance from different angles.