How to calculate power from work or energy and time
The calculator converts your selected work or energy unit to joules and your selected time unit to seconds. It then applies P = W / t and shows the converted values, power results, calculation steps, and a text result you can copy or download.
- Enter a value in Work / energy (W) and choose its Work / energy unit.
- Enter a value in Time (t) and choose its Time unit.
- Click Calculate to show the power, conversions, formula, and result steps.
- Click Copy result or Download result (.txt) after the result appears. Click Reset to clear the inputs and restore Joules (J) and Seconds (s).
Power formula, units, and a worked example
Power is work or energy divided by elapsed time: P = W / t. The result section reports Power in watts, In kW, In hp, In ft·lb/s, and In BTU/h. If you select another input unit, the formula steps include its conversion to joules or seconds.
Work / energy (W): 500
Work / energy unit: Joules (J)
Time (t): 10
Time unit: Seconds (s)
Power: 50 WWith these values, the calculator divides 500 joules by 10 seconds and shows 50 W. The text result also includes the other four displayed power units and the numbered steps.
Power calculator input rules
Work / energy (W) can be zero or positive. Time (t) must be greater than zero. The calculator shows an error for an empty field, a negative work value, zero or negative time, invalid number text, an input above 1e15, or a non-finite result.
Use decimal notation such as 12.5. The number check rejects exponent notation such as 1e3, a leading plus sign, and comma-separated values. Changing an input or unit hides the current result until you click Calculate again.
Where a power calculation comes up
For a physics worksheet, enter the stated work and elapsed time, then copy the formula steps into your notes. The same steps let you check an energy amount given in kilowatt-hours, BTU, or another listed unit after conversion.
For a lab record, download the text result and keep it with the original Work / energy (W), Work / energy unit, Time (t), and Time unit selections.
What the power calculator does not model
The calculation runs in the browser. The calculator script does not send the values you enter to a server. It applies unit conversion and P = W / t to the two supplied values, so it does not model efficiency losses or infer a missing value.
Choose a related science calculator
Use Science Calculators to choose a physics, chemistry, electrical, optics, wave, fluid, gas, or radioactive-decay calculation. Open Work Calculator when force, displacement, and angle are the known inputs for mechanical work.
Open Kinetic Energy Calculator when mass and speed are known and kinetic energy is the unknown. Use Ohm's Law Calculator for electrical voltage, current, resistance, or power inputs.
Frequently asked questions
How do I calculate power from work and time?
Enter Work / energy (W) and Time (t), choose their units, and click Calculate. The calculator converts the selections to joules and seconds, divides with P = W / t, and shows the result and calculation steps.
What units can I use for power calculations?
You can enter Joules (J), Kilojoules (kJ), Calories (cal), Kilocalories (kcal), Foot-pounds (ft·lb), Kilowatt-hours (kWh), or BTU, with Seconds (s), Milliseconds (ms), Minutes (min), Hours (h), or Days.
Why does the power calculator reject my input?
Work / energy (W) must be zero or positive, and Time (t) must be greater than zero. The number check accepts decimal notation, rejects malformed text, and limits each raw input to 1e15. The calculator also rejects a non-finite calculation.
Does the power calculator include efficiency losses?
It applies P = W / t to the values you enter. It does not model efficiency losses or infer a missing value.