Quick answer
Momentum is p = m v. A 1,500 kg car at 25 m/s has a momentum of 37,500 kg·m/s.
Enter mass and velocity. The calculator returns the momentum.
Related tools: Force Calculator: Force from mass and acceleration (Newton's second law). Centripetal Force Calculator: Force and acceleration for circular motion. Normal Force Calculator: Normal force on an object resting on a flat or inclined surface.
How to use the Momentum Calculator
- Enter mass (kg) (above 0).
- Enter velocity (m/s).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Mass | A number, in kg | > 0 |
| Velocity | A number, in m/s | — |
Formula and method
Formula
p = m v
IEEE-754 double precision; shown to the decimals indicated.
Classical (non-relativistic) momentum.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Mass = 1500; Velocity = 25.
| Result | Value |
|---|---|
| Momentum | 37,500 kg·m/s |
Example 2
Inputs: Mass = 0.145; Velocity = 40.
| Result | Value |
|---|---|
| Momentum | 5.8 kg·m/s |
Example 3
Inputs: Mass = 70; Velocity = -3.
| Result | Value |
|---|---|
| Momentum | -210 kg·m/s |
The first line is the headline result (momentum). IEEE-754 double precision; shown to the decimals indicated.
Conservation
In an isolated system total momentum is conserved. If this car hits a stationary 1,500 kg car and they lock together, the pair moves off at 12.5 m/s (37,500 ÷ 3,000).
Direction
Direction is carried by the sign: a car moving the opposite way has negative momentum. Momentum is mass times velocity, so a slow heavy truck can match a fast light car.
Speed units and kinetic energy
Momentum needs velocity in m/s. A speed of 90 km/h is 25 m/s (divide by 3.6), which gives the 1,500 kg car a momentum of 37,500 kg·m/s.
Doubling speed doubles momentum but quadruples kinetic energy: at 25 m/s the car has ½ × 1,500 × 25² = 468,750 J, and at 50 m/s it would have 1,875,000 J.
How the result changes with mass
Holding every other input at the first worked example, this table changes only mass. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Mass | Momentum |
|---|---|
| 750 | 18,750 kg·m/s |
| 1500 | 37,500 kg·m/s |
| 3000 | 75,000 kg·m/s |
| 6000 | 150,000 kg·m/s |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Mass: entering "0" shows "Mass must be greater than 0." beside that field and no result.
- Velocity: left empty shows "Enter velocity." beside that field and no result.
Choosing between the Momentum Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Force Calculator](/science/force-calculator/) | mass and acceleration | Force |
| [Centripetal Force Calculator](/science/centripetal-force-calculator/) | mass, speed and radius | Centripetal force |
| [Normal Force Calculator](/science/normal-force/) | mass, incline angle and gravitational acceleration | Normal force |
| [Net Force Calculator](/science/net-force-calculator/) | force magnitudes and direction of each force | Net force |
| [Friction Force Calculator](/science/friction-force-calculator/) | coefficient of friction μ and normal force | Friction force |
Background: motion and mechanics
For constant acceleration the standard relations are v = u + at, s = ut + ½at², v² = u² + 2as and s = ½(u + v)t. Pick the equation that contains your three known quantities and the one you want. Use SI units (metres, seconds, kilograms, newtons, joules) throughout or the answer will be off by a factor.
These equations stop applying when acceleration changes during the motion, as with a rocket burning fuel; that needs calculus or numerical methods.
Assumptions and limitations
- Direction is carried by the sign
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for mass and velocity to confirm this.
Frequently asked questions
What is the unit of momentum?
Momentum is in kg·m/s, equivalent to newton-seconds; the 1,500 kg car at 25 m/s has 37,500 kg·m/s.
How does impulse relate?
Impulse equals the change in momentum.
Does a heavier object always have more?
Only at equal speed.
How do I convert km/h to m/s?
Divide by 3.6. 90 km/h is 25 m/s.
Does doubling the speed double the momentum?
Yes, momentum is proportional to speed, though kinetic energy grows with the square of speed.
What does the Momentum Calculator calculate?
Linear momentum from mass and velocity. It returns Momentum.
What formula does the Momentum Calculator use?
p = m v. Classical (non-relativistic) momentum.
What do I need to enter in the momentum Calculator?
You enter Mass (kg) and Velocity (m/s).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Direction is carried by the sign.
What is an example of a momentum result?
With mass 1500 and velocity 25, the momentum is 37,500 kg·m/s.
Where does the method come from?
The method follows: OpenStax, University Physics Volume 1 (Rice University): mechanics: linear momentum and collisions.
Related calculators
- Force Calculator — Force from mass and acceleration (Newton's second law).
- Centripetal Force Calculator — Force and acceleration for circular motion.
- Normal Force Calculator — Normal force on an object resting on a flat or inclined surface.
- Net Force Calculator — Resultant of several forces at different angles.
- Friction Force Calculator — Friction force from the coefficient of friction and the normal force.
- Coefficient of Friction Calculator — Coefficient of friction from friction and normal forces.
Sources
- OpenStax, University Physics Volume 1 (Rice University): mechanics: linear momentum and collisions
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.