# Power Calculator (Work and Time)

URL: https://speedycalculator.com/calculators/physics/power-physics/
Last updated: 2026-10-25

> The power calculator finds the rate of doing work, P = W ÷ t, in watts, kilowatts or horsepower. It also converts the result between common power units.

## Inputs

- Work or energy (J, kJ, MJ, cal, kcal, Wh, kWh, BTU)
- Time (s, min, h)

## Results

- Power

## Formula

```
P = W ÷ t
```

## Explanation

Power tells you how quickly energy is used or transferred. Climbing stairs quickly takes more power than climbing slowly, though the work is the same.

### How to use the Power Calculator

- **Work or energy**
- **Time**
- Want to work backwards? Type a value into **Power** and **Time** is calculated for you.

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Divide the work or energy by the time taken.

### Inputs explained

FieldWhat to enterWork or energyUnits: J, kJ, MJ, cal, kcal, Wh …TimeUnits: s, min, h

### Example values

How the main result changes when **Time** changes and everything else stays at the example values above:

Time (s)Power (W)51,0007.5666.671050012.540015333.3320250

## Worked example

Inputs — Work or energy: 5,000 J; Time: 10 s.

Results — **Power = 500 W**.

## FAQ

**How many watts is one horsepower?**
About 745.7 W (mechanical horsepower).

**What is the difference between power and energy?**
Energy is the total amount; power is the rate.

**What formula does the Power Calculator use?**
P = W ÷ t.

**Can I work backwards from the result?**
Yes. Type the result you want into Power and the calculator finds the matching time.


## Sources

- [NIST – Fundamental physical constants](https://physics.nist.gov/cuu/Constants/)