Kinetic Energy Calculator
Compute kinetic energy and momentum.
Results update as you type.
How it works
Kinetic energy is the energy an object carries because it is moving, and this kinetic energy calculator returns it in joules from a mass and a velocity, along with the object's momentum. The faster and heavier something moves, the more kinetic energy it holds, which is precisely the energy that must be absorbed to bring it to a stop. That is why a speeding car is so much harder to halt than a slow one of the same mass. This quantity matters across science and safety: it explains crash severity, the destructive power of a hurricane, the reach of a thrown ball, and how much braking a vehicle needs. Because velocity is squared in the formula, a kinetic energy calculator makes the dramatic effect of speed obvious — doubling velocity quadruples the energy, a fact that shapes speed limits and impact standards. The formula works because kinetic energy equals the accumulated work done accelerating the mass, and that work grows with the square of speed. Momentum, shown alongside, tracks mass times velocity and governs collisions. Physics students, engineers, and safety analysts turn to a kinetic energy calculator to solve motion problems and understand how moving objects behave when they interact.
KE = ½ × mass × velocity²
Kinetic energy is the work needed to accelerate a mass from rest to its current speed, and integrating force over distance yields the one-half mass times velocity squared form. The velocity is squared because doubling speed both doubles the distance covered per second and doubles the momentum change, so energy grows fourfold. Momentum, by contrast, is just mass times velocity and scales linearly with speed.
Source:Standard physics (kinetic energy)
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Worked example
How to use this calculator
- 1
Enter your values
Enter mass and velocity.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Kinetic energy updates instantly as you type — no button to press.
Frequently asked questions
Why is velocity squared in the kinetic energy formula?
Velocity is squared because kinetic energy equals the total work done to accelerate an object, and that work grows with both the force applied and the distance covered, each of which rises with speed. The practical result is dramatic: doubling velocity quadruples kinetic energy, and tripling it multiplies energy by nine. This is why small increases in speed cause disproportionately larger increases in impact energy and stopping distance.
What is the difference between kinetic energy and momentum?
Kinetic energy measures the energy of motion and depends on the square of velocity, while momentum measures the quantity of motion and depends on velocity linearly. Momentum is conserved in every collision, whereas kinetic energy is only conserved in perfectly elastic ones. The calculator shows both because engineers and physicists need momentum to analyse collisions and kinetic energy to understand how much damage or work the motion can produce.
What units does this calculator use?
Enter mass in kilograms and velocity in metres per second. Kinetic energy is then returned in joules, the SI unit of energy, and momentum in kilogram-metres per second. One joule is the energy of a two-kilogram mass moving at one metre per second. If your velocity is given in kilometres per hour, convert it first by dividing by 3.6 to keep the result accurate.
Can kinetic energy be negative?
No. Kinetic energy is always zero or positive because it depends on velocity squared, and squaring any number gives a non-negative result. An object at rest has zero kinetic energy, and any motion gives a positive value regardless of direction. Momentum, by contrast, can be negative because it carries direction, so a value's sign there indicates which way the object is travelling.
How does kinetic energy relate to stopping distance?
Braking must remove all of an object's kinetic energy, and since that energy scales with the square of speed, stopping distance rises sharply as speed increases. A car travelling twice as fast carries four times the kinetic energy and needs roughly four times the distance to stop under the same braking force. This squared relationship is the physical reason speed limits have such a large effect on crash outcomes.