Kinetic Energy CalculatorFree online other calculator — instant results, no sign-up
Calculate nonrelativistic kinetic energy from mass and speed.
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About the Kinetic Energy Calculator
The Kinetic Energy Calculator calculates the energy of motion from an object's mass in kilograms and speed in meters per second. It uses the nonrelativistic formula KE = ½mv² and reports the result in joules. With the default mass of 10 kg and speed of 5 m/s, the kinetic energy is 125 J.
- Mass (kg)
- The object's mass in kilograms (kg), with a default value of 10 kg.
- Speed (m/s)
- The magnitude of the object's velocity in meters per second (m/s), with a default value of 5 m/s.
Formula and method
KE = ½mv² = ½ × 10 kg × (5 m/s)² = 125 J
- KEKinetic energy, measured in joules (J).
- mThe object's mass, measured in kilograms (kg).
- vThe object's speed relative to the chosen reference frame, measured in meters per second (m/s).
Square the speed, multiply by the mass, and divide by two. For the default inputs, squaring 5 m/s gives 25 m²/s²; multiplying by 10 kg and dividing by two gives 125 kg·m²/s², equivalent to 125 J.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Mass10 kg
- Speed5 m/s
Results
- Result125 J
How to use the Kinetic Energy Calculator
- 1Enter the object's mass in Mass (kg), or keep the default of 10 kg.
- 2Enter its speed in Speed (m/s), or keep the default of 5 m/s.
- 3Check that both inputs are nonnegative and expressed in the specified units.
- 4Run the calculation to evaluate KE = ½mv².
- 5Read the kinetic energy result in joules; the default inputs produce 125 J.
Reading your result
The Result row shows the object's kinetic energy in joules (J). A result of 125 J means the 10 kg object moving at 5 m/s has 125 joules of energy due to its translational motion in the chosen reference frame. One joule equals one kg·m²/s².
Limitations
This formula assumes classical, nonrelativistic motion and is appropriate when speed is much smaller than the speed of light. It treats the object as a particle or describes its center-of-mass translational motion; it does not include additional rotational kinetic energy, internal energy, or potential energy. Mass and speed should be nonnegative, and the result depends on the reference frame used to measure speed. Output accuracy is limited by the accuracy of the inputs.
Common questions
Why does speed have a stronger effect than mass on kinetic energy?+
Mass enters the formula linearly, while speed is squared. Doubling mass at the same speed doubles kinetic energy, but doubling speed at the same mass quadruples it.
Can I enter speed in km/h or mass in grams?+
Convert them first: divide km/h by 3.6 to obtain m/s, and divide grams by 1,000 to obtain kilograms. This calculator's formula assumes kilograms and meters per second.
Does the direction of motion change the result?+
No. Kinetic energy is a scalar and depends on speed, not direction. Objects with the same mass and speed have the same kinetic energy in the same reference frame, even if they move in opposite directions.
Does this calculator include the energy of a rolling object's rotation?+
No. Using the object's mass and center-of-mass speed calculates only translational kinetic energy. For a rolling object, total kinetic energy also includes rotational energy, calculated separately as ½Iω², where I is moment of inertia and ω is angular speed.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
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Results are estimates for informational purposes and are not financial, medical or legal advice.