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KE Calculator | Calculate kinetic energy from mass and velocity

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Calculate kinetic energy from mass and speed with the formula KE = ½mv², showing why speed matters more than mass. Results are given in joules and foot-pounds with real-world context — ideal for physics homework, vehicle safety and engineering estimates.

Last updated: June 2026 · Free · No sign-up required

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Results

Enter values above and click Calculate to see your result instantly.

Quick reference

ObjectMassSpeedKE
Baseball pitch0.145 kg40 m/s116 J
10 kg mass10 kg5 m/s125 J
Cyclist80 kg10 m/s4,000 J
Car1,500 kg27 m/s (60 mph)546,750 J

info KE Calculator (Kinetic Energy)

Free math calculator — enter your numbers and get an instant, accurate result.

info Private by design

Everything runs locally in your browser. No uploads, no accounts, no tracking.

info Works everywhere

Fully responsive and mobile-friendly — calculate on any device, any time.

info Educational

Includes the formula and step-by-step explanation so you understand the math, not just the answer.

Interpretation guide

ChangeEffect on KE
Double the massKE doubles (linear)
Double the speedKE quadruples (squared)
Triple the speedKE × 9
Halve the speedKE ÷ 4 — why small speed cuts matter in crashes

lightbulb Worked example: car at highway speed

A 1,500 kg car travels at 30 m/s (108 km/h). How much kinetic energy does it carry? KE = ½ × 1500 × 30² = 750 × 900 = 675,000 J = 675 kJ. In watt-hours: 675,000 / 3600 ≈ 187.5 Wh.

Result: 675,000 joules (675 kJ) of kinetic energy.

What this means: That is 187.5 Wh — enough to run a 100 W bulb for nearly two hours, all carried as motion. At 15 m/s the same car holds just 168,750 J: halving the speed quarters the energy, which is why crash severity climbs so steeply with speed.

Formula & methodology

Formula: KE = ½ × m × v² (m in kg, v in m/s, KE in joules)

How kinetic energy is computed

Kinetic energy is the energy of motion:

KE = ½ × m × v²

  • Mass converts to kilograms (1 lb = 0.4536 kg) and velocity to m/s (1 mph = 0.4470 m/s) before calculating.
  • The result is in joules: 1 J = 1 kg·m²/s².
  • Because velocity is squared, doubling speed quadruples the energy.

Reading the result

A 1,500 kg car at 30 m/s carries ½ × 1500 × 900 = 675,000 J (675 kJ) — about 187.5 watt-hours, enough to run a 100 W bulb for nearly two hours. The same car at 15 m/s holds just 168.75 kJ, which is why speed dominates crash severity.

Authoritative source: Wolfram MathWorld

Frequently asked questions

What is the kinetic energy formula?
The KE Calculator (Kinetic Energy) uses the standard KE = ½ × m × v² (m in kg, v in m/s, KE in joules). You enter your values, and the calculator applies the formula step by step, showing the working so you can verify the math and understand how the result is derived rather than trusting a black box.
What is the KE of 10 kg moving at 5 m/s?
The KE Calculator (Kinetic Energy) is free, private, and accurate: it runs entirely in your browser (no uploads, no accounts), applies the standard calculation, and explains each step so you can verify the result. KE Calculator (Kinetic Energy) is a free online calculator that helps you work out ke (kinetic energy) quickly and accurately, right in your browser. There is no limit on usage, and it works on any device.
Why does speed matter more than mass?
Kinetic energy is KE = ½mv² — the speed is squared while the mass is not, so doubling the speed quadruples the energy, while doubling the mass only doubles it. That is why a car crash at 60 mph is four times more energetic than the same car at 30 mph. Speed is the dominant factor in impact energy, which is why speed limits matter so much for safety.
Can I enter pounds and mph?
Yes — the calculator accepts imperial inputs and converts them to the standard SI units (kilograms and metres per second) internally before applying KE = ½mv². Enter the mass in pounds and the speed in mph, and the tool returns the kinetic energy in joules as well as in foot-pounds for a more intuitive sense of scale.
What is a joule in everyday terms?
One joule is roughly the energy needed to lift a small apple about one metre, or the energy of a 1 kg object moving at about 1.4 m/s. A dietary calorie is about 4,184 joules, a moving car carries millions of joules, and a rifle bullet carries a few thousand. The calculator gives joules plus foot-pounds so the numbers connect to familiar experiences.
How much energy does a car carry at highway speed?
A 1,500 kg car at 30 m/s (108 km/h) has KE = ½ × 1500 × 30² = 675,000 J, or 675 kJ. That is about 187.5 watt-hours — enough to run a 100 W bulb for nearly two hours. Drop to 15 m/s and the energy falls to 168.75 kJ, which is why speed dominates crash severity.
Why is velocity squared instead of just doubled?
Work = force × distance, and stopping distance grows with v² because a faster object both carries more momentum and needs more distance to decelerate. Doubling speed from 10 to 20 m/s quadruples the kinetic energy. This v² relationship is also why braking distances roughly quadruple when speed doubles.
What is a joule compared to a calorie?
One joule is the energy of lifting about 102 g (a small apple) by one meter against gravity. A food Calorie (kilocalorie) is 4,184 J — so a 100-Calorie snack holds about 418 kJ, comparable to the 675 kJ in our car example. Mechanical and food energy use the same unit, just at very different scales.
Does kinetic energy include direction?
No — kinetic energy is a scalar: ½mv² uses speed, not velocity, so a car moving north at 20 m/s has the same KE as one moving south at 20 m/s. Direction matters for momentum (p = mv, a vector) and for collisions, but the energy available to do damage depends only on mass and speed.

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