Kinetic Energy Calculator
Kinetic energy calculator: E = ½mv². Find energy from mass and speed, or the speed or mass from a known energy.
Ek = ½ · m · v²
How to use this calculator
- Choose the quantity you want under “Solve for”.
- Type the known values and pick their units: any combination works.
- The result updates as you type. Open “Show the steps” to see the substitution.
Kinetic energy is the energy of motion, Ek = ½·m·v². Doubling the speed quadruples the energy, which is why braking distance grows so fast with speed.
Results can be shown in joules, kilojoules, calories, kWh or electronvolts.
Formula
Ek = ½ · m · v²
| Symbol | Quantity | Units |
|---|---|---|
| m | Mass | kg, g, mg, µg, t, lb, oz, st, US ton, ct, Da |
| v | Speed | m/s, km/h, mph, kn, ft/s, c |
| Ek | Kinetic energy | J, kJ, MJ, cal, kcal, Wh, kWh, eV, BTU, erg, ft·lbf |
Worked example
Given: m = 1 000 kg · v = 20 m/s
Ek = ½ · m · v²
Result: Ek = 200 kJ
Frequently asked questions
How much kinetic energy does a 1,000 kg car have at 72 km/h?
72 km/h = 20 m/s, so E = ½ · 1000 · 20² = 200 kJ.
Why does speed matter more than mass?
Energy grows with the square of speed but only linearly with mass.