Enter the work output and the total heat input of a heat engine into the calculator to determine the thermal efficiency.

Thermal Efficiency Formula

The following formula is used to calculate the thermal efficiency.

ηth = W / Q
  • Where ηth is the thermal efficiency
  • W is the work output (J)
  • Q is the heat input (J)

To calculate the thermal efficiency, divide the system work output by the heat input.

Thermal Efficiency Definition

Thermal efficiency is the ratio of the work output to the heat input of a heat engine. In other words, the efficiency at which the engine converts heat to mechanical work.

Thermal Efficiency Example

How to calculate thermal efficiency?

  1. First, determine the input heat.

    Measure the total heat put into the engine. For this example, we will say this is 10 J of heat.

  2. Next, determine the workout output.

    Measure the total work produced by the engine. For this example, the work is 9 J.

  3. Finally, calculate the thermal efficiency.

    Using the formula we find the thermal efficiency to be 9/10 = .90 = 90%


What is thermal efficiency?

Thermal efficiency is the rate or efficiency at which a heat engine converts heat to work.

Can something be 100% thermal efficient?

No, in reality, heat engines will always have some losses associated with them.

thermal efficiency formula