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Physics formula

How to calculate momentum

Momentum measures how much motion an object has based on its mass and velocity.

See the formulaOpen calculator
Direct answer
Formula
p = m * v

Use the table below to match each symbol with the right input. Keep units consistent before you start.

Momentum formula
Start here when you only need the equation and variable names.
Formula
p = m * v

Momentum measures how much motion an object has based on its mass and velocity.

Variable meanings
Check each symbol, meaning, and unit before you calculate.
SymbolNameDescriptionUnit
pMomentumQuantity of motion.kg*m/s
mMassObject mass.kg
vVelocityObject velocity.m/s
When to use this formula
Check that your situation matches the formula before you trust the result.
  • Good for collisions, impulse, and motion problems where mass and velocity are known.
Step-by-step method
Follow these steps when you are solving it by hand.
  1. 1Convert mass to kilograms.
  2. 2Convert velocity to meters per second.
  3. 3Multiply mass by velocity.
  4. 4Keep direction if velocity has one.
Examples
These sample numbers show the order of operations and units.
Ball
m
2 kg
v
15 m/s
  1. 1.p = 2 * 15
  2. 2.p = 30 kg*m/s
Result
The momentum is 30 kg*m/s.
Car
m
1,200 kg
v
20 m/s
  1. 1.p = 1200 * 20
  2. 2.p = 24000 kg*m/s
Result
The momentum is 24,000 kg*m/s.
Mistakes to avoid
Small input or unit errors can change the answer a lot.
  • Mixing metric and imperial units before solving the momentum formula.
  • Forgetting squared units such as m^2, m/s^2, or velocity squared.
  • Dropping negative signs when direction matters.
  • Rounding measured values too early in the calculation.
Open the Momentum Calculator
Open the calculator for the answer without rewriting the formula.

Enter your values in the related calculator, then compare the output with the hand method above.

Open Momentum Calculator
FAQs
Short answers for common formula questions.
Can I calculate Momentum by hand?

Yes. Write the units next to each value, convert rates or measurements first, and round only the final answer.

Why does my Momentum result differ from another calculator?

Most differences come from rounding, unit conversions, rate timing, or a slightly different version of the formula.

When is the Momentum Calculator better than hand math?

Open the Momentum Calculator to check several scenarios or skip the hand arithmetic.