Momentum Calculator

Enter the mass and speed of an object to find its momentum.

This result is an estimate only. Double-check important figures before relying on them.

How it is calculated

Momentum (kg·m/s) = mass (kg) × speed (m/s)
If you enter km/h, the speed is divided by 3.6 first

To see the energy of the same motion, use the kinetic energy calculator.

Worked example

A 1,000 kg car at 72 km/h:

Speed = 72 ÷ 3.6 = 20 m/s
Momentum = 1,000 × 20 = 20,000 kg·m/s

Why your number may differ

The result is the size of the momentum in a straight line. For collisions you must treat direction as positive or negative, and add the objects together.

Frequently asked questions

What is the formula for momentum?

Momentum = mass × velocity. With mass in kilograms and speed in metres per second, the unit is kg·m/s.

Is momentum the same as kinetic energy?

No. Momentum grows in direct proportion to speed, while kinetic energy grows with the square of the speed.

Does direction matter?

Yes, momentum is a vector. This calculator gives the size only, for motion in one direction.