What is the kinetic energy formula?

Kinetic energy equals one half times the mass times the speed squared. Because speed is squared, doubling the speed gives four times the kinetic energy.

What units does it use?

Mass in kilograms and speed in metres per second give kinetic energy in joules. A 1000 kilogram car at 28 metres per second has about 390,000 joules of kinetic energy.

Why does speed matter so much?

Because kinetic energy depends on the square of the speed, small increases in speed mean large increases in energy, which is why higher speeds are so much more dangerous in a crash.

Kinetic Energy Calculator

This kinetic energy calculator finds the energy an object has because it is moving, using the formula that kinetic energy equals one half times the mass times the speed squared. Kinetic energy is one of the central ideas in physics, the energy of motion that a moving object can transfer when it hits something or does work, and it is measured in joules. You choose whether to solve for the kinetic energy, the mass or the speed, then enter the other two values. To find the energy the calculator multiplies half the mass by the square of the speed; to find the mass it divides twice the energy by the speed squared; and to find the speed it takes the square root of twice the energy divided by the mass. The key feature of the formula is that speed is squared, so kinetic energy grows very quickly with speed: doubling the speed quadruples the energy, which is exactly why a crash at 100 kilometres per hour is far more than twice as severe as one at 50. Use kilograms for mass and metres per second for speed to get an answer in joules. This is a staple of mechanics and a powerful way to understand road safety, sport and impacts. Enter your two known values to see the result straight away.

Solve for

Mass (kg)

Speed (m/s)

Kinetic energy (J)

392,000 J

kinetic energy

Mass in kilograms and speed in metres per second give joules. Estimate only.

How it works

The calculator uses kinetic energy equals one half m v squared. To find the energy it squares the speed, multiplies by the mass and halves it. To find the mass it divides twice the energy by the speed squared, and to find the speed it takes the square root of twice the energy over the mass.

Worked example

A 1000 kilogram car at 28 metres per second, about 100 kilometres per hour, has a kinetic energy of half times 1000 times 28 squared, which is 392,000 joules, or 392 kilojoules.

Related calculators

Potential Energy Calculator: stored energy.
Force Calculator: F equals m a.
Velocity Calculator: speed and distance.
Energy Converter: joules, calories, kWh.

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