Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Calculate the kinetic energy of a moving object from its mass and velocity.
9.0000 J
Kinetic energy is the energy an object has due to its motion. This tool calculates it from mass and velocity.
Enter mass (kg) and velocity (m/s). Kinetic energy appears instantly in joules (J).
KE = ½ × mass × velocity²
Because velocity is squared, speed dominates the result far more than mass does. Doubling the mass doubles the kinetic energy, but doubling the velocity multiplies it by four, and tripling the velocity multiplies it by nine. You can see this by running the same mass through the tool at different speeds and comparing the joules. This is the physics behind why stopping distances grow so quickly at higher speeds, and why a small, fast object can carry as much energy as a large, slow one.
Take a hypothetical 1,200 kg car. At 15 m/s, the calculation is 0.5 × 1,200 × 15² = 0.5 × 1,200 × 225 = 135,000 J, or 135 kJ. At 30 m/s the calculation is 0.5 × 1,200 × 900 = 540,000 J. The speed doubled and the energy quadrupled from 135,000 J to 540,000 J. Neither figure includes air resistance, rotating parts or anything else, only the energy of straight-line motion of the whole mass.
Since velocity is squared, entering a negative velocity gives exactly the same kinetic energy as the positive value. Energy is a scalar, so it has no direction. If you enter a negative mass the tool will still multiply through and show a negative energy, but that has no physical meaning, so it is best to keep mass positive. The calculator does not block these entries; it just performs the arithmetic and shows four decimal places.
The formula applies to everyday speeds well below the speed of light. It treats the object as a single mass moving as a whole, so a rolling wheel has extra rotational energy not captured here. It also does not tell you what happens in a collision, since real impacts depend on how the energy is absorbed by materials. Any use of the figure for safety, engineering or accident analysis should be checked by a qualified professional.
Kinetic energy links directly to work: the work done by a net force on an object equals its change in kinetic energy. You can pair this tool with the Work/Energy Calculator to see how much force over a distance is needed to bring an object up to a given speed, and with the Power Calculator to see how quickly that energy must be delivered.
Kinetic energy grows with the square of velocity -- doubling speed quadruples kinetic energy, a key reason higher speeds are disproportionately more dangerous in collisions.
No. Velocity is squared, so a negative velocity gives the same kinetic energy as the same speed in the positive direction.
Divide the km/h value by 3.6 to get meters per second. For example, 108 km/h becomes 30 m/s.
Vehicles combine large mass with sizable speed, and speed is squared. A 1,200 kg car at 30 m/s carries 540,000 J, far more than a small object at walking pace.
No. It calculates only the straight-line motion energy of the whole mass as half of mass times velocity squared.
Reference: NIST Weights and Measures