Thermal Efficiency Calculator

The Ceiling No Real Engine Can Exceed

Carnot efficiency defines the absolute theoretical maximum thermal efficiency for any heat engine operating between two temperatures, a benchmark real engines are always measured against.

The Formula

Efficiency % = (1 − Tcold / Thot) × 100

Both temperatures must be in Kelvin (absolute temperature).

Worked Example

An engine operating between a hot reservoir at 900 K and a cold reservoir at 300 K:

Efficiency = (1 − 300/900) × 100 = 66.7%

How to Use This Calculator

Enter the Hot Reservoir Temperature in Kelvin.
Enter the Cold Reservoir Temperature in Kelvin.
Select Calculate to get the ideal maximum efficiency.

Related Calculations

Need real-world combustion efficiency instead of the ideal limit? See the Combustion Efficiency Calculator, or check adiabatic flame temperature in the Adiabatic Flame Temperature Calculator.