ConverterHub

Momentum Calculator

Find an object’s momentum.

How it is calculated

Linear momentum is the product of mass and velocity: p = m × v. Mass m is entered in kilograms and velocity v in metres per second, so p comes out in kg·m/s. Momentum is a vector, so its sign follows the direction of the velocity: a negative velocity gives a negative momentum, which simply means motion in the opposite direction. The tool accepts any numbers, including zero and negatives, and rounds the result to two decimals. It uses the classical formula, valid when the speed is far below the speed of light, and it gives no impulse or collision result.

Worked example

A car with a mass of 1,200 kg travelling at 25 m/s, which is 90 km/h. p = 1,200 × 25 = 30,000.00 kg·m/s. Doubling the speed would double the momentum, while doubling the mass would also double it.

Try this example →

Common mistakes

  • Entering the speed in km/h: convert first, by dividing by 3.6, so 90 km/h becomes 25 m/s.
  • Entering the mass in grams or tonnes when the field expects kilograms.
  • Confusing momentum with kinetic energy: energy grows with the square of speed, momentum only linearly.
  • Dropping the sign when two objects move in opposite directions and then adding the magnitudes in a collision.
  • Using the formula at speeds close to the speed of light, where relativistic momentum is needed.

About this calculator

This calculator applies the basic mechanics formula p = mv (momentum equals mass times velocity), giving a vector quantity measured in kg·m/s that describes how hard an object is to stop.

Physics students use it for homework on collisions and conservation of momentum problems, while it also explains everyday intuitions like why a slow-moving truck is harder to stop than a fast-moving ball — mass matters as much as speed. The calculator keeps direction/sign in mind where relevant, since momentum is a vector, so an object moving in the negative direction produces negative momentum in one-dimensional problems.

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