Physics
Efficiency
A ratio with no units. Multiply by a hundred for a percentage, or keep the decimal for further calculation.
The Formula
efficiency = useful output / total input
A ratio with no units. Multiply by a hundred for a percentage, or keep the decimal for further calculation.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| eta | Efficiency | ratio | Fraction of input that becomes useful output. |
| Eout | Useful output | J or W | Energy or power delivered in the wanted form. |
| Ein | Total input | J or W | All energy or power supplied. |
What Each Symbol Means
etaratio
Efficiency
Fraction of input that becomes useful output.
EoutJ or W
Useful output
Energy or power delivered in the wanted form.
EinJ or W
Total input
All energy or power supplied.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate efficiency page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Efficiency, filed under Science. Every number the guide produces comes from substituting into this one line.