How the kinetic energy calculator works
Enter mass and speed to calculate kinetic energy with KE = ½ × m × v². The calculator converts the selected values to kilograms and meters per second, applies the classical formula, and shows the calculation steps.
Enter mass and speed
Use the visible controls in this order:
- Enter a value in Mass (m), then choose a Mass unit: Kilograms (kg), Grams (g), Pounds (lb), Slugs, or Metric tons (t).
- Enter a value in Speed (v), then choose a Speed unit: Meters per second (m/s), Kilometers per hour (km/h), Miles per hour (mph), Feet per second (ft/s), or Knots.
Mass must be greater than zero. Speed must be zero or greater. Enter ordinary decimal notation; scientific notation is rejected. Each input value must be no greater than 1e12.
Calculate, copy, download, or reset the result
- Click Calculate to display the result and the intermediate steps.
- Review the visible result cards, then click Copy result to copy the text output or Download result (.txt) to save it as a text file.
- Click Reset to clear both inputs, restore
kgandm/s, clear any error, and hide the result.
Invalid input displays an error and hides the result. The result cards show joules, kilojoules, kilocalories, foot-pounds, kilowatt-hours, and BTU. Calories are included in the copied and downloaded text output.
Units and result output
The unit selectors convert mass and speed before the calculation. The visible cards use J, kJ, kcal, ft·lb, kWh, and BTU. The text output also includes calories in cal.
Calculation limits
This tool uses the classical, non-relativistic formula KE = ½ × m × v². It does not calculate relativistic or rotational kinetic energy, potential energy, or other forms of energy. It rejects invalid input, input values above 1e12, and any calculated result that is not finite.
Privacy and calculation behavior
The calculation runs in browser JavaScript, and the calculation code does not submit the entered values. This describes the calculator logic only; the page also loads external analytics scripts.
Frequently Asked Questions
What is the formula for kinetic energy?
Kinetic energy equals one half times mass times speed squared: KE = ½ × m × v². This is the classical (non-relativistic) formula for the energy of a moving object due to its motion.
What units does this calculator support?
Mass can be entered in Kilograms (kg), Grams (g), Pounds (lb), Slugs, or Metric tons (t). Speed can be entered in Meters per second (m/s), Kilometers per hour (km/h), Miles per hour (mph), Feet per second (ft/s), or Knots. Visible result cards show joules, kilojoules, kilocalories, foot-pounds, kilowatt-hours, and BTU; the copied and downloaded text also includes calories.
Why does kinetic energy increase with the square of speed?
Because speed appears as v² in the formula, doubling the speed quadruples the calculated kinetic energy, while tripling it increases the result ninefold.
Can speed be negative or zero in this calculator?
Speed must be zero or a positive number. An input of zero produces zero kinetic energy, while a negative speed is rejected. Mass must be greater than zero.
Does this calculator account for relativistic effects?
No. It applies the classical formula and does not compute relativistic kinetic energy for objects approaching the speed of light.