Loading calculator...
- Finds the kinetic energy of a moving object from its mass and velocity.
- Can also find the mass or the velocity.
- Works with kg, g, lb and m/s, km/h, mph.
- Shows the energy in joules, kJ, kcal and ft·lb, plus momentum.
How to use the kinetic energy calculator
Choose what to find
Kinetic energy, mass or velocity.
Enter the two known values
For example 1,000 kg and 20 m/s.
Pick the units
For mass, velocity and energy.
Read the result
With conversions and the formula used.
The kinetic energy formula
Kinetic energy is the energy an object has because it is moving. It grows with mass, and much faster with speed: doubling the speed makes the kinetic energy four times larger.
Kinetic energy formulas
KE = ½ × m × v²
m = 2 × KE ÷ v²
v = √(2 × KE ÷ m)
With mass in kg and velocity in m/s, the energy is in joules.
Example 1: a car
1,000 kg moving at 20 m/s (72 km/h).
- Kinetic energy 200,000 J = 200 kJ
- Momentum 20,000 kg·m/s
Example 2: a baseball
0.145 kg thrown at 90 mph (40.2336 m/s).
- Kinetic energy 117.36 J
Where kinetic energy matters
Physics class
Solve energy and work problems.
Road safety
See why speed raises crash energy so sharply.
Sports
Compare the energy of balls, bats and athletes.
Engineering
Size brakes, flywheels and barriers.
Find the force on an object with the force calculator, its acceleration with the acceleration calculator, or its flight path with the projectile motion calculator.
Kinetic energy calculator FAQ
What is the formula for kinetic energy?
KE = ½mv², where m is mass in kg and v is velocity in m/s.
What unit is kinetic energy measured in?
Joules (J). One joule is one kg·m²/s².
What happens to kinetic energy if speed doubles?
It becomes four times larger, because the velocity is squared.
What is the kinetic energy of a 1,000 kg car at 72 km/h?
200,000 J, or 200 kJ.
Can kinetic energy be negative?
No. Mass is positive and velocity is squared, so it is always zero or positive.
What is the difference between kinetic energy and momentum?
Momentum is mass × velocity and has a direction; kinetic energy is ½mv² and has none.