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Kinetic Energy Calculator

Computes the translational kinetic energy of a moving mass from KE = ½·m·v², reported in joules, kilojoules, kilowatt-hours and kilocalories.

When to use

You need the energy of motion of an object of known mass and speed (vehicle, projectile, ball), for example to compare impact or braking energies.

Do not use when: Rotation contributes significantly (rotational energy ½·I·ω² is not included), speeds approach the speed of light (relativistic formula needed), or you need energy from height (use potential-energy).

Formula

KE = ½ × mass_kg × velocity_m_s²; kJ = J / 1000; kWh = J / 3,600,000; kcal = J / 4184

Inputs

Parameter	Type	Unit	Required	Description
`mass_kg`	number	kg	yes	Mass of the moving object in kilograms. Range: > 0
`velocity_m_s`	number	m/s	yes	Speed in metres per second (km/h ÷ 3.6, mph × 0.44704). Limited to 10 % of the speed of light, below which the classical formula is accurate to within 1 %. Range: ≥ 0, ≤ 30000000

Outputs

Output	Type	Unit	Description
`kinetic_energy_j`	number	J	KE = ½ × m × v².
`kinetic_energy_kj`	number	kJ	Kinetic energy in kilojoules.
`kinetic_energy_kwh`	number	kWh	Kinetic energy in kilowatt-hours (J ÷ 3,600,000).
`kinetic_energy_kcal`	number	kcal	Kinetic energy in kilocalories (thermochemical, J ÷ 4184).
`velocity_km_h`	number	km/h	The input speed in km/h.

Example

1200 kg car at 25 m/s (90 km/h): {"mass_kg":1200,"velocity_m_s":25} → {"kinetic_energy_j":375000,"kinetic_energy_kj":375,"kinetic_energy_kwh":0.104167,"kinetic_energy_kcal":89.6272,"velocity_km_h":90}

0.145 kg baseball at 40 m/s: {"mass_kg":0.145,"velocity_m_s":40} → {"kinetic_energy_j":116,"kinetic_energy_kj":0.116,"velocity_km_h":144}

GET https://tttkmbb.com/api/v1/calculate/kinetic-energy?mass_kg=1200&velocity_m_s=25

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/kinetic-energy (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/kinetic-energy · Markdown: https://tttkmbb.com/physics/kinetic-energy.md · JSON definition: https://tttkmbb.com/physics/kinetic-energy.json
MCP: server https://tttkmbb.com/mcp, tool calculate_kinetic_energy
OpenAPI operationId: calculate_kinetic_energy
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

HyperPhysics – Kinetic energy (reference)
Wikipedia – Kinetic energy (reference)
NIST Special Publication 811 – Guide for the Use of the SI, Appendix B (conversion factors) (standard)

FAQ

Why does doubling the speed quadruple the energy?

Kinetic energy scales with the square of speed (v²), which is why braking distance and crash severity rise much faster than speed.

Does direction matter?

No. Kinetic energy is a scalar; only the magnitude of the velocity (speed) enters the formula.

Related calculators

Momentum Calculator — Momentum p = m·v of the same object.
Potential Energy Calculator — Energy stored by height, exchanged with kinetic energy in free fall.
Work & Power Calculator — Work needed to produce this energy change.