Kinetic Energy Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/5/2026
The kinetic energy of a moving object is calculated with Ec = ½ × mass × speed². For a 2 kg mass moving at 10 m/s, the kinetic energy is 100 joules.
Explanation
Kinetic energy is the energy an object has purely because it's moving: the heavier it is and the faster it goes, the greater this energy. The notable point in the formula Ec = ½mv² is that speed is squared, not just multiplied: doubling an object's speed quadruples its kinetic energy, for the same mass. This relationship is exactly why a vehicle's braking distance grows so fast with speed, or why a high-speed impact is disproportionately more dangerous than a low-speed one. This formula assumes constant speed (no acceleration during the measurement) and only applies as written at speeds far below the speed of light — more than enough for all everyday uses. For the weight of this same object at rest, rather than its energy in motion, see our weight calculator.
Example: a 2 kg mass at 10 m/s
Inputs
Mass: 2 kg. Speed: 10 m/s.
Calculation
Kinetic energy = 0.5 × 2 × 10² = 0.5 × 2 × 100 = 100.
Result
This object has a kinetic energy of 100 joules.
Frequently asked questions
Why is speed squared in this formula?
It's a fundamental physical property of motion, not an arbitrary choice: the energy needed to accelerate an object to a given speed grows with the square of that speed. In practice, doubling a car's speed quadruples its kinetic energy (and therefore, with the same braking force, its stopping distance).
Does this formula work at any speed?
It holds with excellent accuracy at all speeds encountered in everyday life and classical engineering. It stops being exact only at speeds close to the speed of light, where Einstein's special relativity takes over — a case outside the scope of this calculator.
What's the difference from potential energy?
Kinetic energy depends on motion (mass and speed), while potential energy depends on an object's position within a force field, for example its height in Earth's gravitational field. A stationary object at height has potential energy but no kinetic energy.