Kinetic Energy Calculator — KE = ½mv²
Kinetic energy is the energy an object has because it is moving: KE = ½mv². Enter any two of energy, mass and speed and the calculator finds the third.
Notice the squared speed: doubling the speed quadruples the kinetic energy. That single fact explains why braking distances grow so fast with speed and why high-speed collisions are so destructive.
Use the calculator
Enter any TWO values — the calculator solves the third.
The formula
KE = ½mv² — so m = 2KE/v² and v = √(2KE/m). Energy is measured in joules (J).
Worked example
Worked example: A 2 kg ball moves at 6 m/s. KE = ½ × 2 × 6² = 36 J. At 12 m/s it would be ½ × 2 × 144 = 144 J — four times as much.
Frequently asked questions
Why is speed squared in the kinetic energy formula?
Because kinetic energy comes from the work done accelerating the object, and work involves force times distance; distance grows with the square of speed under constant acceleration, which produces the v² term.
Can kinetic energy be negative?
No. Mass is positive and v² is always positive, so KE is zero or positive. An object at rest has zero kinetic energy.
What speed gives 1 kg an energy of 50 J?
v = √(2KE/m) = √(2 × 50/1) = √100 = 10 m/s — about 36 km/h.