Kinetic energy is the energy of a moving object: KE = ½mv². It quantifies the work required to accelerate (or decelerate) the object.
KE = ½ × m × v² (joules) v = √(2 × KE / m) p = m × v (momentum); KE = p²/(2m)
m — mass (kg)
v — velocity (m/s)
KE — kinetic energy (J)
p — momentum (kg·m/s)
Worked example: 1,500 kg car at 60 km/h (16.67 m/s). KE = 0.5 × 1,500 × 16.67² = 0.5 × 1,500 × 277.8 = 208,333 J = 208 kJ. Same car at 120 km/h has 4× the KE (833 kJ) — KE scales with v².
KE for common objects
Object
Mass
Velocity
Kinetic energy
Tennis ball serve
57 g
200 km/h (55.6 m/s)
88 J
Bullet (9 mm)
8 g
365 m/s
533 J
Cricket ball (fast bowl)
163 g
144 km/h (40 m/s)
130 J
Cyclist
80 kg
30 km/h (8.3 m/s)
2,760 J
Car at 60 km/h
1,500 kg
16.67 m/s
208 kJ
Car at 120 km/h
1,500 kg
33.33 m/s
833 kJ
Boeing 747 at cruise
350,000 kg
250 m/s
10,938 MJ
Standard / source: Classical Newtonian mechanics; relativistic correction needed only above ~0.1c.
This calculator uses the standard kinetic energy calculator formula:
Kinetic Energy Formula
KE = ½ × m × v²
Frequently Asked Questions
What is kinetic energy?⌄
Kinetic energy is the energy an object possesses due to its motion. KE = ½mv², where m = mass in kg and v = velocity in m/s. Units: joules (J).
What is the kinetic energy of a 70 kg person running at 5 m/s?⌄
KE = ½ × 70 × 5² = ½ × 70 × 25 = 875 J.
How does velocity affect kinetic energy?⌄
Kinetic energy is proportional to the square of velocity. Doubling speed increases kinetic energy by 4×. This is why vehicle crash severity increases dramatically with speed.
What is the difference between kinetic and potential energy?⌄
Kinetic energy is energy of motion; potential energy is stored energy due to position or state (e.g. gravitational PE = mgh). Total mechanical energy = KE + PE.
What units is kinetic energy measured in?⌄
The SI unit is the joule (J). One joule = 1 kg·m²/s². For larger values, kilojoules (kJ) or kilocalories (kcal) are used.
How does mass affect kinetic energy?⌄
Kinetic energy is directly proportional to mass. Doubling the mass doubles the kinetic energy at the same speed.
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Energy goes with the SQUARE of speed. Doubling speed quadruples kinetic energy — and quadruples the braking distance. This is the single most under-appreciated fact in road safety.
Independently verified
12 July 2026 — Formula re-derived from first principles and verified numerically against hand-computed reference cases, including edge cases and unit handling.
Results are for guidance. Verify against the current edition of the governing standard and have a qualified professional review before use in practice.