Energy from power and time calculator
Calculate energy from power and time. Enter the two known values in the stated SI units and see the formula and result.
Result for the values shown.
Calculations run in your browser.
What to enter
| Input | Meaning and units |
|---|---|
| Power (W) | Enter power in W; use the same basis as the other measurements. |
| Time (s) | Enter time in s; use the same basis as the other measurements. |
Understanding your result
Read Energy (J) in the units and model stated on this page. The formula energy = power × time defines the relationship; measurement accuracy and model applicability are separate from numerical precision.
Common mistakes
- Mixing input units or changing the physical meaning of a variable without changing the model.
Check your calculation
- Use the worked example as a known reference case, then change one input at a time and check the direction and units of the response.
Calculation checks, sources and review limits
What is the energy given the power and time?
Calculate energy from power and time. Enter the two known values in the stated SI units and see the formula and result.
Common uses
- Find the unknown energy from two known measurements.
- Check unit consistency before using power, energy & time.
How it works
Start with power = energy ÷ time. Rearrange the relationship to energy = power × time. Enter power in W and time in s; the result is energy in J. Values must be nonnegative and any denominator must be positive. The model assumes consistent quantities and units. Energy divided by elapsed time gives average power over that interval. It does not describe instantaneous power when the rate varies.
Worked example
Power: 2 W; Time: 5 s gives energy: 10 J.