Energy Calculator

Calculate kinetic energy from mass and velocity, or potential energy from mass and height.

By Konstantin Iakovlev · Updated September 2026 · Source: Khan Academy

Energy Type

Energy

125.00 J

Energy Calculation

FormulaKE = 0.5 x m x v^2
Energy125.00 Joules
In kJ0.1250 kJ

Use the Energy Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only. Results are estimates based on the information you provide and the assumptions described on this page.

How It Works

Mass and velocity give an object's kinetic energy, and mass and height give its gravitational potential energy; this calculator computes one or the other, depending on the Energy Type you pick. Quantifying energy is what lets engineers design systems precisely and run the safety analyses that head off costly failures.

Three physics relationships drive the results. Kinetic Energy (KE), the energy of motion, comes from 0.5 * mass * velocity^2. Potential Energy (PE) follows mass * gravitational acceleration * height, with g taken as 9.81 m/s^2, the standard value of 9.80665 m/s^2 rounded to two decimals. Total mechanical energy is KE plus PE; the calculator shows one at a time, so run it in both modes and add the two results.

Unit consistency is where results go wrong; mixing grams for mass with kilometers per hour for velocity will hand you nonsense. The gravitational acceleration constant also gets dropped or misapplied, particularly when potential energy is being worked out for other planetary environments. This tool stays within mechanical energy and makes no attempt to capture thermal, chemical, or other forms.

Example: Mechanical Energy of a Delivery Drone

  1. 1 A delivery drone with a mass of 5 kg flies at 20 m/s at an altitude of 100 meters. How much mechanical energy does it carry?
  2. 2 Kinetic mode: enter mass 5 and velocity 20. KE = 0.5 × 5 × 20^2 = 0.5 × 5 × 400 = 1,000.00 J (1.0000 kJ).
  3. 3 Potential mode: keep mass 5 and enter height 100. PE = 5 × 9.81 × 100 = 4,905.00 J (4.9050 kJ). Adding the two runs gives a total mechanical energy of 1,000 + 4,905 = 5,905 J.
  4. 4 This is the energy stored in the drone's motion and height, not a measure of battery use: a multirotor also spends power continuously to hold itself up and to overcome air drag, and none of that appears in KE or PE.

Source: Khan Academy · Last updated: September 2026

Frequently Asked Questions

What is the formula for kinetic energy?
Kinetic energy equals one-half times mass times velocity squared (KE = 1/2 mv^2). The unit is joules (J) when mass is in kilograms and velocity in meters per second. Doubling the velocity quadruples the kinetic energy.
What is the difference between kinetic and potential energy?
Kinetic energy is the energy of motion, while potential energy is stored energy due to position or configuration. Gravitational potential energy equals mass times gravity times height (PE = mgh). Total mechanical energy is the sum of both.
How do I convert between joules and other energy units?
One joule equals 0.239 calories, 0.000278 watt-hours, or 0.738 foot-pounds. One kilowatt-hour equals 3,600,000 joules. One food calorie (kcal) equals 4,184 joules.

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