Calculate kinetic energy from mass and speed, or the mass or speed from the energy. Momentum is shown too.
Last updated: November 8, 2026
The energy of motion
Kinetic energy is the energy an object has because it is moving: • KE = ½ × m × v² • m = 2 × KE ÷ v² • v = √(2 × KE ÷ m) • Momentum: p = m × v Example: a 1,000 kg car at 20 m/s (about 45 mph) has ½ × 1,000 × 20² = 200,000 J = 200 kJ of kinetic energy. Because energy grows with the square of speed, doubling the speed quadruples the energy. That is why crashes at high speed are so much more destructive.
Common questions about kinetic energy
KE = ½ × m × v². With mass in kg and speed in m/s, the result is in joules (J).
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In kilograms.
In metres per second.