Kinetic Energy Calculator (KE = ½·m·v²)

Compute the kinetic energy of a moving object from its mass and speed. Result in joules with kcal and ft·lb conversions.

Inputs

In kilograms (kg). E.g. 1500 kg ≈ a small car.

27.78 m/s ≈ 100 km/h ≈ 62 mph.

Result

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How to use this calculator

  • Enter the mass in kilograms.
  • Enter the speed in metres per second. Convert from mph if needed: v(m/s) = mph × 0.447.
  • Read kinetic energy in joules and useful unit conversions.

About this calculator

Kinetic energy is the energy an object carries because it is moving. It scales linearly with mass but with the square of speed — doubling the speed quadruples the KE. That is why crash severity rises so sharply with speed: a car at 60 mph carries four times the kinetic energy of the same car at 30 mph. The formula KE = ½·m·v² comes from integrating force over distance using Newton's second law. Kinetic energy is converted to heat, sound, and deformation in collisions, and to potential energy when an object is lifted.

Frequently asked

Why does KE scale with v² and not v?+
Because work (force × distance) is needed to accelerate. Stopping distance grows linearly with speed, but the force × distance integral grows quadratically. That is also why braking distance roughly quadruples when you double speed.
How does KE compare to potential energy?+
Both are forms of mechanical energy and convert into each other. A roller coaster trades PE (height) for KE (speed) and back. The total stays constant if friction is negligible.
What is a typical car's KE at highway speed?+
A 1500 kg car at 27.78 m/s (100 km/h) carries ~579 kJ of kinetic energy — enough to lift the same car about 39 metres straight up.
Does this work for rotating bodies?+
No — this formula is for translational motion. Rotating bodies have a separate rotational KE = ½·I·ω² where I is the moment of inertia and ω the angular velocity.
Relativistic correction?+
At speeds near light, the classical formula understates the true KE. Use KE = (γ − 1)·m·c² where γ = 1/√(1 − v²/c²). Below 10% of light speed the difference is < 0.5%.

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