Carnot Efficiency Calculator

About this calculator

This calculator finds the theoretical Carnot efficiency of a heat engine: η = 1 − Tc/Th, where Tc and Th are the absolute (Kelvin) temperatures of the cold and hot reservoirs. This is the maximum efficiency any heat engine can achieve between those two temperatures, as set by the second law of thermodynamics — no real engine can exceed it.

Mechanical and thermal engineers use it as a benchmark when designing power plants, engines, or refrigeration cycles, comparing a real machine's actual efficiency against this theoretical ceiling to see how much room for improvement remains. Physics students use it to build intuition for the second law. Enter the hot and cold reservoir temperatures to get the maximum possible efficiency.