This kinetic energy calculator finds the energy of a moving object from its mass and speed, and can solve backwards for speed.
Physics
Kinetic Energy Calculator
Calculate kinetic energy from mass and velocity.
Calculator
About this calculator
Formula notes
KE = ½·m·v², so v = √(2·KE/m). Doubling speed quadruples the energy.
Worked examples
- Example: a 1000 kg car at 20 m/s carries KE = ½×1000×400 = 200000 J = 200 kJ.
- A 1,500 kg vehicle travelling at 20 m/s has kinetic energy 0.5 x 1500 x 20^2 = 300,000 J.
How to use it
- Enter the mass and velocity (or energy and one other).
- Use kilograms and m/s for joules.
- Read the kinetic energy or solved variable.
Frequently asked questions
Why is stopping distance so much worse at high speed?
Energy scales with v², so brakes must dissipate four times the energy at double speed.
Can kinetic energy be negative?
No. Mass and v² are always non-negative, so KE ≥ 0.
Limits and interpretation
- The classical formula omits rotational energy, deformation, gradients, drag, and relativistic effects.
- Because velocity is squared, measurement error in speed has an amplified effect on calculated energy.