Kinetic Energy Calculator
Kinetic energy is the energy an object possesses due to its motion, defined by the formula KE = ½mv². A 1 kg object moving at 1 m/s has exactly 0.5 joules of kinetic energy. Because kinetic energy scales with the square of velocity, doubling speed quadruples the energy — which is why high-speed collisions are so destructive. This calculator solves the kinetic energy equation in all three directions: given mass and velocity, find KE; given KE and velocity, find mass; given KE and mass, find velocity. It also computes rotational kinetic energy (KE_rot = ½Iω²) for spinning objects like flywheels and wheels. Built-in presets cover common scenarios: bullets, vehicles, baseballs, and bicycles. Results include momentum (p = mv) and comparisons to everyday objects to help you understand the magnitude.
bolt Kinetic Energy Inputs
analytics Results
tips_and_updates Tips
- • KE scales with v² — doubling speed quadruples kinetic energy, which is why stopping distance grows rapidly with speed.
- • 1 joule = 1 kg·m²/s² = 0.7376 ft·lb = 0.239 calories. Firearms ballistics commonly use ft·lb; physics uses joules.
- • For bullets, grain is the common mass unit: 1 grain = 0.0648 g. A 150-grain bullet at 2800 ft/s has ~2600 ft·lb of muzzle energy.
- • Rotational KE depends on the moment of inertia — a solid disk has I = ½mr², a hoop has I = mr², a solid sphere has I = (2/5)mr².
- • Kinetic energy is a scalar (not a vector) — it's always positive and has no direction, unlike momentum.
How to Use This Calculator
Pick What to Solve For
Choose whether you want to find kinetic energy, mass, or velocity. You can also switch to rotational KE mode for spinning objects.
Enter Inputs with Units
Type in the two known values and pick units — mass in kg/g/lb/oz/grain, velocity in m/s/km/h/mph/ft/s, energy in J/kJ/ft·lb/calories. Or load a preset (bullet, car, baseball, bicycle).
Review the Results
The primary result displays in multiple units. You also get momentum (p = mv) and comparisons to everyday objects.
The Formula
Kinetic energy is proportional to mass and to the square of velocity. A car traveling at 60 km/h has four times the kinetic energy it would have at 30 km/h. The work-energy theorem states that the net work done on an object equals its change in kinetic energy: W = ΔKE. Rotational kinetic energy follows the same quadratic form but uses moment of inertia and angular velocity in place of mass and linear velocity.
KE = ½ × m × v² | KE_rot = ½ × I × ω² | p = m × v
lightbulb Variables Explained
- KE Kinetic energy in joules (J) = kg·m²/s²
- m Mass in kilograms (kg)
- v Velocity in meters per second (m/s)
- I Moment of inertia in kg·m² (rotational)
- ω Angular velocity in rad/s (rotational)
- p Momentum in kg·m/s = m × v
tips_and_updates Pro Tips
KE scales with v² — doubling speed quadruples kinetic energy, which is why stopping distance grows rapidly with speed.
1 joule = 1 kg·m²/s² = 0.7376 ft·lb = 0.239 calories. Firearms ballistics commonly use ft·lb; physics uses joules.
For bullets, grain is the common mass unit: 1 grain = 0.0648 g. A 150-grain bullet at 2800 ft/s has ~2600 ft·lb of muzzle energy.
Rotational KE depends on the moment of inertia — a solid disk has I = ½mr², a hoop has I = mr², a solid sphere has I = (2/5)mr².
Kinetic energy is a scalar (not a vector) — it's always positive and has no direction, unlike momentum.
Frequently Asked Questions
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All formulas verified against official standards.