BYTETOOLS

Kinetic Energy Calculator

Calculate kinetic energy from mass and velocity with KE = ½mv², or solve for mass or speed. Results in joules, kilojoules, calories and foot-pounds.

385,802.4691 J
Kinetic energy
385.8025
Kilojoules
92,209.0031
Calories
284,553.2983
Foot-pounds
1,000 kg
Mass
27.7778 m/s (100 km/h)
Speed

Working

KE = ½ × 1,000 kg × (27.7778 m/s)² = 385,802.4691 J. Because velocity is squared, doubling the speed quadruples the energy. Conversions: 1 cal = 4.184 J, 1 ft·lbf = 1.35582 J.

What is the Kinetic Energy Calculator?

The ByteTools Kinetic Energy Calculator solves KE = ½ × m × v² for any of the three variables: energy, mass or velocity.

  • Solves KE = ½mv² for KE, m or v
  • Mass in kg, g, lb or tonnes; speed in m/s, km/h, mph, ft/s
  • Output in J, kJ, cal and ft·lbf
  • Shows the quadratic effect of velocity on energy
  • Worked formula printed with each answer
  • 100% private — runs entirely in your browser

How to use the Kinetic Energy Calculator

  1. 1

    Choose what to solve for: energy, mass or velocity.

  2. 2

    Enter the two known values with your preferred units.

  3. 3

    Read the result in joules plus kJ, calories and foot-pounds.

  4. 4

    Note the worked formula displayed under the result.

  5. 5

    Copy the answer with one click.

About the Kinetic Energy Calculator

The ByteTools Kinetic Energy Calculator solves KE = ½ × m × v² for any of the three variables: energy, mass or velocity. Enter mass in kilograms, grams, pounds or tonnes and speed in m/s, km/h, mph or ft/s — the tool converts everything to SI internally and reports the energy in joules, kilojoules, calories (1 cal = 4.184 J) and foot-pounds (1 ft·lbf = 1.35582 J).

Because velocity is squared, doubling speed quadruples kinetic energy — which is why braking distances and crash energies grow so quickly with speed. The calculator states the substituted formula with every answer so students can follow the working.

It suits physics coursework, vehicle and projectile energy estimates, and quick engineering checks. Everything runs 100% locally in your browser: no uploads, no tracking of your numbers, and it works offline.

Frequently asked questions

How do you calculate kinetic energy?

Kinetic energy is half the mass times the velocity squared: KE = ½mv². A 1,000 kg car at 27.78 m/s (100 km/h) carries KE = ½ × 1000 × 27.78² ≈ 385,800 J, or about 386 kJ. Mass must be in kilograms and speed in m/s to get joules.

Why does doubling speed quadruple kinetic energy?

Because velocity is squared in the formula. At 2× the speed, v² is 4× as large, so the energy — and roughly the braking distance needed to shed it — is 4× as large. That quadratic growth is why small speed increases matter so much in road safety.

How do I find velocity from kinetic energy?

Rearrange the formula: v = √(2 × KE ÷ m). An object of 2 kg carrying 100 J moves at √(200 ÷ 2) = 10 m/s. The calculator does this automatically when you choose to solve for velocity.

Can kinetic energy be negative?

No. Mass is positive and v² is never negative, so kinetic energy is always zero or positive. Direction of motion does not matter — a car moving backwards at 20 m/s has exactly the same kinetic energy as one moving forwards at 20 m/s.

What is a foot-pound of energy?

One foot-pound (ft·lbf) is the energy needed to lift one pound-force through one foot — exactly 1.3558179 joules. It is the customary unit for firearm muzzle energy in the US, which is why this calculator includes it alongside joules and calories.

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