Efficiency Table: Efficiency by Useful output
Reference table of efficiency for Efficiency across a range of useful output values — exact, engine-computed figures you can read off at a glance.
Efficiency Calculator
Verified formula Updated Jun 2026 Private — runs on your device
Verified formula
Private
Efficiency
80.00%
- Energy lost
- 20.00
For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.
How to use the Efficiency Calculator
The Efficiency Calculator works out your efficiency, along with 1 related figure in an instant. Enter useful output and total input and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.
- Enter the useful output.
- Enter the total input.
- Read off your efficiency, together with energy lost — the calculator updates automatically, with no button to press.
Formula
The Efficiency Calculator uses the formula:
Efficiency = Useful output ÷ Total input × 100
Worked example
For example, with useful output of 80 and total input of 100, the efficiency is 80.00%.
| Useful output | 80 |
|---|---|
| Total input | 100 |
| Efficiency | 80.00% |
|---|---|
| Energy lost | 20.00 |
Results are estimates for educational use, not professional advice.
Frequently asked questions
Divide useful output by total input and multiply by 100. 80 out of 100 is 80% efficient.
No. For real machines, some energy is always lost, so efficiency is always below 100%.
It is the input that does not become useful output, usually escaping as heat, sound or friction.
Yes. Use the same energy or power units for input and output, and it applies to engines, motors and processes.
Enter the useful output. Enter the total input. Read off your efficiency, together with energy lost — the calculator updates automatically, with no button to press.
Related guides
How to Calculate Efficiency: Formula, Steps & Examples
Learn how to calculate Efficiency — the formula explained step by step, with worked examples and a free calculator to check your answer.