Carnot Efficiency Calculator

The Carnot efficiency is one of the deepest results in all of physics: it sets the absolute ceiling on how much heat any engine can ever turn into useful work, and this calculator computes it from the two temperatures the engine runs between. Enter the temperature of the hot reservoir, where heat comes in, and the cold reservoir, where waste heat is dumped, choose kelvin or Celsius, and it returns the Carnot efficiency as a fraction and a percentage, with the temperatures shown in kelvin so you can check the working. What makes the result so striking is that it depends on nothing but those two temperatures. The design of the engine, the fuel, the working fluid, the cleverness of the engineering, none of it can push the efficiency past one minus the cold temperature divided by the hot temperature. Every real engine, hampered by friction, turbulence and heat loss, falls short of this limit, so the Carnot value is the gold standard against which actual performance is judged. The formula also reveals why power stations use very hot steam and why engines run hotter for more efficiency: the bigger the temperature gap, the higher the ceiling. A crucial detail is that the temperatures must be absolute, measured in kelvin from absolute zero, which is why the calculator converts any Celsius input by adding 273.15 before applying the formula, a step that trips up many students. That makes the tool genuinely useful for physics and engineering students learning thermodynamics and the second law and checking homework, and for anyone comparing the theoretical limit of a heat engine, power cycle or heat pump with its real efficiency. The formula and a worked example are explained clearly below.

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