Enter any two of three values — Work (in joules), Power (in watts), or Time (in seconds) — and the Work and Power Calculator solves for the missing third using the formula P = W / t. You can also calculate Work from Force and Distance using W = F·d·cos(θ), or find Power from Force and Velocity with P = F·v. Results include all three quantities with unit breakdowns.
Result
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Work
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Power
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Time
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Work (kWh)
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Power (kW)
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Power (hp)
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Power is calculated by dividing the total work done by the time taken: P = W / t. For example, if 9000 joules of work is done in 60 seconds, the power is 9000 / 60 = 150 watts. Power tells you how fast energy is being transferred.
Rearrange the formula P = W / t to get t = W / P. So if you know the work done (in joules) and the power (in watts), divide work by power to get the time in seconds. For example, 9000 J ÷ 150 W = 60 seconds.
Work is measured in joules (J), which can also be expressed as kg·m²/s² in SI units, or in kilowatt-hours (kWh). Power is measured in watts (W), equivalent to joules per second (J/s), or in kilowatts (kW) and horsepower (hp).
There are 1,000 joules in one kilojoule (kJ). So to convert kilojoules to joules, multiply by 1,000. For example, 9 kJ = 9,000 J.
One horsepower (hp) equals 746 watts, which means a machine running at 1 hp delivers 746 joules of energy per second. Over one hour, that equals 746 × 3600 = 2,685,600 joules (approximately 2.686 MJ).
The angle θ represents the angle between the direction of the applied force and the direction of motion. Only the component of force parallel to the motion does work, so cos(θ) scales the result. At 0° (force fully along the motion), cos(θ) = 1 and all force contributes. At 90°, cos(θ) = 0 and no work is done.
Joules per second is the definition of a watt (W), the SI unit of power. When 1 joule of work is done in 1 second, the power output is 1 watt. This relationship is captured in the formula P = W / t.
When a constant force F acts on an object moving at a constant velocity v in the direction of the force, power is simply P = F × v. This is useful when you know force and speed rather than total work and time. The result is in watts when force is in newtons and velocity is in m/s.