Physics formula
How to calculate power
Power measures how quickly work is done or energy is transferred.
Direct answer
Formula
P = W / t
Use the table below to match each symbol with the right input. Keep units consistent before you start.
Power formula
Start here when you only need the equation and variable names.
Formula
P = W / t
Power measures how quickly work is done or energy is transferred.
Variable meanings
Check each symbol, meaning, and unit before you calculate.
| Symbol | Name | Description | Unit |
|---|---|---|---|
| P | Power | Rate of doing work. | W |
| W | Work | Energy transferred. | J |
| t | Time | Elapsed time. | s |
When to use this formula
Check that your situation matches the formula before you trust the result.
- Power is the right formula when you know the work or energy transferred and how long it took.
Step-by-step method
Follow these steps when you are solving it by hand.
- 1Use work in joules.
- 2Use time in seconds.
- 3Divide work by time.
- 4Report the result in watts.
Examples
These sample numbers show the order of operations and units.
Short lift
W
600 J
t
3 s
- 1.P = 600 / 3
- 2.P = 200 W
Result
The power is 200 W.
Machine output
W
180,000 J
t
120 s
- 1.P = 180000 / 120
- 2.P = 1500 W
Result
The power is 1,500 W.
Mistakes to avoid
Small input or unit errors can change the answer a lot.
- Mixing metric and imperial units before solving the power formula.
- Forgetting squared units such as m^2, m/s^2, or velocity squared.
- Dropping negative signs when direction matters.
- Rounding measured values too early in the calculation.
Open the Work and Power Calculator
Open the calculator for the answer without rewriting the formula.
Enter your values in the related calculator, then compare the output with the hand method above.
Open Work and Power CalculatorFAQs
Short answers for common formula questions.
Can I calculate Power by hand?
Yes. Write the units next to each value, convert rates or measurements first, and round only the final answer.
Why does my Power result differ from another calculator?
Most differences come from rounding, unit conversions, rate timing, or a slightly different version of the formula.
When is the Work and Power Calculator better than hand math?
Open the Work and Power Calculator to check several scenarios or skip the hand arithmetic.