Efficiency Calculator
Enter the useful output and total input (in matching units, such as energy, work, or power) to calculate a system’s efficiency as a percentage.
What is efficiency?
Efficiency measures how much of the energy or work put into a system comes out as useful output, rather than being lost to friction, heat, resistance, or other unwanted forms.
The formula
Efficiency is calculated as η = (Useful Output ÷ Total Input) × 100%, using matching units for input and output (both in joules, both in watts, both in dollars of value, etc.). No real system reaches 100% efficiency because some energy is always converted to a non-useful form, most commonly waste heat.
This is a general-purpose efficiency formula applicable to mechanical, electrical, or thermal systems alike, as long as input and output are measured consistently. This calculator is for general reference and educational purposes.