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Physics Tools · Updated October 21, 2026 · Reviewed by FormatFlow Editorial

Kinetic Energy Calculator

You can calculate kinetic energy from an object's mass and velocity, with gram or kilogram inputs, m/s or km/h speeds, and the result shown in joules and kilojoules.

Runs in your browserFree · No sign-up · No watermark
Mass + speed → EnergyRuns in your browser
Loading the tool…

Everything runs locally in this tab. No file is uploaded while the tool loads.

This tool runs in your tab. Nothing is uploaded and no copy is stored.

How files are handled

At a glance

Works with
Mass + speed → Energy
Processing
In your browser
Price
Free, no account
Updated
October 21, 2026
All Physics Tools

About Kinetic Energy Calculator

Kinetic energy is the energy of motion: KE = ½ × m × v². Because velocity is squared, speed dominates the result. Doubling the speed multiplies the energy by four, which is why a small increase in vehicle speed matters so much in collision energy. Mass counts linearly, so doubling mass only doubles the energy.

Enter mass in grams or kilograms and velocity in m/s or km/h, and the calculator converts both to SI units before applying the formula. The result is shown in joules and kilojoules, with the substituted working and the conversion behind it. It covers translational kinetic energy only, not rotation or deformation.

What this tool does

The details that matter when you use Kinetic Energy Calculator for real work.

  • Mass in grams or kilograms

    Enter the mass in either unit; it is converted to kilograms before the formula runs.

  • Speed in m/s or km/h

    Enter the velocity in either unit, and the calculator converts it to meters per second automatically.

  • Joules and kilojoules

    The headline is in joules, with kilojoule and megajoule equivalents for larger values.

  • The square is made visible

    The substituted working shows the velocity being squared, which makes the effect of changing speed easy to see.

  • Formula shown

    KE = ½ × m × v² is printed with your values substituted, so the result can be checked line by line.

  • Copy the answer

    Copy the energy in joules as a plain number for notes, a spreadsheet or a homework answer.

How to use Kinetic Energy Calculator

No account, no installation — the whole job happens in this browser tab.
  1. 01

    Enter the mass

    Use grams or kilograms and choose the matching unit from the selector.

  2. 02

    Enter the velocity

    Use meters per second or kilometers per hour; the sign does not matter because the velocity is squared.

  3. 03

    Read the energy

    The headline shows the kinetic energy in joules, with kilojoules and megajoules underneath for larger values.

  4. 04

    Check the squared velocity

    The working panel shows the conversion to SI units and the substitution of mass and velocity squared into the formula.

  5. 05

    Copy or reset

    Copy the energy value, or press Reset to clear the mass and velocity fields.

How this tool works

Works with
Mass + speed → Energy
Processing
Client-side, in your browser. Nothing is uploaded.
Requirements
Chrome, Edge, Firefox or Safari · JavaScript enabled

Limitations worth knowing

  • Translational kinetic energy only; rotational energy and energy stored in deformation are not included.
  • Relativistic effects are ignored, so the formula is accurate for everyday speeds but not for particles moving close to the speed of light.
  • The result is only as accurate as the mass and velocity entered; the displayed digits are rounded.
  • Assumes the mass and velocity describe one rigid object rather than a system with internal movement.

Privacy and file handling

Mass and velocity values are processed entirely in your browser. Nothing is uploaded, stored or logged, and no network request is made while you calculate.

Read the full privacy policy

Kinetic Energy Calculator FAQ

Short, direct answers to the questions people ask before using this tool.
Why is velocity squared in the kinetic energy formula?
Kinetic energy comes from the work done to accelerate an object from rest: with a constant force over a distance that grows with the square of speed, the work ends up proportional to v². That is why the formula is ½ × m × v² rather than proportional to speed alone.
How do I convert km/h to m/s for this calculator?
Divide the speed in km/h by 3.6, because one kilometer is 1,000 meters and one hour is 3,600 seconds. You do not have to convert by hand: choose km/h in the velocity unit selector and the calculator performs the same conversion before applying the formula.
What is the difference between kinetic energy and momentum?
Kinetic energy is a scalar proportional to the square of velocity, while momentum is a vector proportional to velocity. Two objects can have the same momentum but different kinetic energies if their masses differ, which is why both quantities are used in collision analysis.
Why does doubling the speed quadruple the kinetic energy?
The velocity is squared in the formula. Replacing v with 2v multiplies the energy by 2² = 4, while doubling the mass only multiplies it by 2. That is the physical reason stopping distances grow so quickly with speed.
Does the direction of motion affect kinetic energy?
No. Velocity is squared, so a negative velocity produces the same positive energy as the same speed in the opposite direction. Kinetic energy is a scalar, even though velocity is a vector.
What is a joule in kinetic energy calculations?
A joule is the SI unit of energy, equal to one kilogram times one square meter per second squared, or one newton of force acting over one meter. A kilojoule is 1,000 joules, and a megajoule is one million joules.
Does this kinetic energy calculator include rotational energy?
No. The formula covers translational kinetic energy, the energy of an object moving from place to place. A rolling wheel or a spinning flywheel also has rotational kinetic energy, which depends on its moment of inertia and angular velocity.
Why are results also shown in kilojoules and megajoules?
Energy values for cars, projectiles and machinery quickly reach tens of thousands of joules, where long digit strings are hard to read. Kilojoules and megajoules are the same value with a scale prefix, so the headline stays readable without changing the physics.

Background reading

Format guides that explain the trade-offs behind Kinetic Energy Calculator.