Four calculators, one panel.
Pick a mode below — mix and match units freely, everything recalculates live as you type, and every result explains itself.
How heavy the moving object is.
How fast it's moving. Direction doesn't matter — only speed.
The known kinetic energy of the object.
Must be greater than zero to solve for speed.
The known kinetic energy of the object.
Must be non-zero to solve for mass.
Any energy amount — not just kinetic energy — converts the same way.
Two inputs to an answer.
No manual required — but here's the entire flow in four moves.
Pick a mode
Kinetic energy for mass + speed → KE. Solve velocity or Solve mass for the two reverse cases. Unit converter for switching between any energy units on their own.
Enter what you know
Type a number and pick its unit from the dropdown right next to it — mix kilograms with km/h, or pounds with mph, it's all converted automatically. The example chips fill everything in with one tap.
Read the results
The main answer sits up top in large type. Related values in other units sit below, and the exact formula with your numbers substituted sits at the bottom.
Trust the checks
Impossible inputs — negative mass, a zero mass or velocity you're trying to divide by — get flagged with a plain-English reason instead of a wrong or broken answer. Copy any result set with one click.
One formula, three ways to use it.
Every mode above is the same equation, just solved for a different letter.
Kinetic energy
Mass in kilograms, velocity in metres per second, energy comes out in joules (kg·m²/s²).
Solving for velocity
Divide the kinetic energy by the mass, double it, then take the square root.
Solving for mass
Double the kinetic energy and divide by the square of the velocity.
Questions people actually ask.
The short answers — with the long ones one tap away.
What is the formula for kinetic energy?+
Kinetic energy is KE = ½ × m × v², where m is mass in kilograms and v is velocity in metres per second. The result comes out in joules. A 2 kg object moving at 3 m/s has KE = 0.5 × 2 × 3² = 9 J.
How do I calculate the kinetic energy of a moving object?+
Enter the object's mass and velocity in the Kinetic energy tab, in whatever units you have — kilograms or pounds, m/s or km/h. The calculator converts everything to kilograms and metres per second, applies the formula, and shows the answer in joules, kilojoules, calories, kWh, eV, ft·lb and BTU.
How do I find velocity from kinetic energy?+
Rearrange the formula: v = √(2 × KE ÷ m). Enter the known kinetic energy and mass in the Solve velocity tab and the calculator returns speed in m/s, km/h, mph, ft/s and knots.
How do I find mass from kinetic energy?+
Rearrange the formula: m = 2 × KE ÷ v². Enter the known kinetic energy and velocity in the Solve mass tab and the calculator returns mass in kilograms, grams, pounds and ounces.
What units is kinetic energy measured in?+
The SI unit is the joule (J), equal to 1 kg·m²/s². Other common units include the kilojoule, calorie, kilocalorie, kilowatt-hour, electronvolt, foot-pound and BTU. The Unit converter tab switches between all of them instantly.
Does kinetic energy depend on direction?+
No — kinetic energy is a scalar, not a vector. It only depends on speed, not direction. Because velocity is squared in the formula, moving backward at a given speed produces exactly the same kinetic energy as moving forward at that speed, and the result is always zero or positive.
Is this tool free, and where does my data go?+
It's completely free and runs entirely in your browser — nothing you type is uploaded, logged, or sent to any server. No account, no sign-up, no limits.