Efficiency Calculator

Your details

Enter any two of output, input, and efficiency, and the calculator finds the third.
The useful energy or power the system delivers, for example 750 W of mechanical power. Use the dropdown to pick any energy or power unit.
The total energy or power supplied to the system. It may use a different unit from the output, but must be the same kind (both energy or both power).
For heat engines, compare your result to the maximum efficiency allowed by thermodynamics.
Put a price on the energy lost as waste over a period of operation.
Currency
EfficiencyHigh efficiency
75%
Energy lost (waste)25%
75% %
Very low<25Low25-50Moderate50-75High75-90Very high90+

This system is 75.0% efficient.

  • Efficiency is the useful output divided by the total input, expressed as a percentage.
  • About 25.0% of the input is lost, typically as waste heat, friction, or sound.
  • The same formula works for energy (joules) or power (watts) as long as both sides use the same quantity type.

Next stepReducing losses through better insulation, lubrication, or design pushes efficiency toward its practical ceiling.

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