Carnot Efficiency Calculator

About this calculator

The Carnot efficiency, η = 1 − Tc/Th, sets the theoretical maximum efficiency of any heat engine operating between a hot reservoir at absolute temperature Th and a cold reservoir at Tc, both measured in kelvin. Sadi Carnot derived this limit in 1824 from an idealized reversible cycle of isothermal and adiabatic steps, proving that no real engine — regardless of its working fluid or mechanical design — can exceed it without violating the second law of thermodynamics.

Mechanical and thermal engineers use the Carnot limit as a benchmark to judge how close a real engine, turbine or refrigeration cycle comes to its theoretical best, since actual efficiencies are always lower due to friction, heat leakage and irreversible processes. Power plant designers apply it to justify raising boiler temperatures for higher efficiency, and physics students use it to build intuition for the second law before studying real cycles like Rankine or Otto.