Momentum Calculator
Momentum calculator (p = mv): solve for momentum, mass or velocity in SI units, with a US/imperial readout. Curriculum-aligned.
Momentum Calculator
Enter any two values and leave the third blank — the calculator solves for it. Momentum is in kg·m/s; results are in SI units.
- Curriculum
- English (global) — Cambridge International + IB
- Built against
- Cambridge IGCSE / A-Level Physics + IB Diploma (2023–2025) — Momentum & Impulse
- Unit system
- SI primary; US/imperial readout below
- First published
- 2 Jun 2026
- Last updated
- 4 Sep 2026
View authoritative scientific sources
- NIST SP 811 (2008), §3 — units & conversions
- BIPM SI Brochure, 9th edition (2019)
- Momentum — Encyclopædia Britannica
⚠️ Educational use only — see full disclaimer
EDUCATIONAL USE DISCLAIMER
This calculator is provided for educational and reference purposes only. It is not a substitute for instruction from a qualified teacher, your prescribed textbook, or your school's official curriculum materials.
When preparing for examinations, always cross-check our calculations and notation against your current syllabus and your teacher's guidance. Syllabus conventions and accepted notation vary between curricula and may change between examination years.
If you believe any calculation, notation, or curriculum reference in this tool is inaccurate, please let us know via the feedback button. We review feedback promptly and update tools when verified corrections are needed.
RECATOOLS accepts no liability for academic, examination, professional, or research outcomes arising from use of this tool.
How to Use the Momentum Calculator
Pick your curriculum
Use the curriculum pills above to match your syllabus (Cambridge/IB, 高考 or SBMPTN). Terminology and the whole page follow your selection.
Enter any two values
Type two of momentum, mass and velocity — leave the one you want to find blank. Mass and velocity have unit selectors.
Read the SI result
The answer is shown in SI units — kg·m/s, kg, m/s — with a dimmed US/imperial readout for mass and velocity.
Check against your syllabus
The Tool Information block shows exactly which syllabus this is built against. Spot something off? Use the feedback button.
Momentum, in Your Curriculum's Words
Momentum (p = mass × velocity)
Example: An object of mass 2.0 kg moves at 3.0 m/s. Find its momentum.
Given: m = 2.0 kg, v = 3.0 m/s. Using p = mv:
p = 2.0 × 3.0 = 6.0 kg·m/s
Momentum is a measure of an object's "quantity of motion": p = mv, the product of its mass and velocity. Its SI unit is the kilogram-metre per second (kg·m/s). Because velocity is a vector, momentum is also a vector — it has the same direction as the velocity. Rearranged, the same relation gives mass (m = p / v) or velocity (v = p / m), which is why this tool solves for whichever value you leave blank.
Impulse (J = FΔt) equals the change in momentum: J = Δp. In a collision, the total momentum of an isolated system is conserved — the law of conservation of momentum. Momentum has no direct imperial equivalent, so it is shown in SI only; mass and velocity carry a dimmed US/imperial readout. All calculation happens in your browser — nothing is uploaded.
Momentum is conserved in every collision — which is why a gun recoils backward as the bullet flies forward.
10 Facts About Momentum
Momentum is p = mv, measured in kg·m/s.
Momentum is a vector quantity — it has direction.
Impulse equals the change in momentum, J = Δp.
Total momentum is conserved in an isolated system.
Conservation of momentum explains rocket propulsion.
In an elastic collision, KE and momentum are both conserved.
In an inelastic collision, only momentum is conserved.
Force = rate of change of momentum (Newton's second law).
A heavy slow object can have the same momentum as a light fast one.
This calculator runs in your browser — your working stays private.
Frequently Asked Questions
- p = mv — momentum equals mass times velocity. Rearranged, m = p / v and v = p / m. The calculator solves for whichever value you leave blank and shows the answer in kg·m/s. Momentum is a vector, so its direction is the same as the velocity's.
- The SI unit of momentum is the kilogram-metre per second (kg·m/s). Mass is in kilograms (kg), velocity in metres per second (m/s). You may enter other units for mass and velocity (g, lb, km/h, mph); the tool converts to SI. Momentum has no direct imperial equivalent, so it is shown in SI only.
- Impulse (force × time interval) equals the change in an object's momentum, J = Δp. This is the impulse-momentum theorem: a force acting for a time changes the momentum by the impulse delivered.
- In an isolated system (no external forces), the total momentum before and after an event such as a collision is the same. This principle holds for both elastic and inelastic collisions and is one of the most fundamental conservation laws in physics.
- The physics — p = mv in SI units — is identical worldwide. What changes is the terminology; "momentum" is 动量 in Chinese, while SBMPTN students see the Indonesian term. The calculated value is the same.
- Yes. Enter two of momentum, mass and velocity and leave the third blank — the calculator rearranges p = mv and solves for the missing value.
- The Tool Information block lists the exact syllabus for your selected curriculum (e.g. SBMPTN/SNBT Fisika). It is a study aid, not a substitute for your official syllabus or teacher.
- No. Every calculation runs in your browser; nothing you type is uploaded. It works offline once the page has loaded.
- Completely free, no account or usage limit. It runs entirely in your browser and collects no data.
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Method & sources
How it computes
p = mv and J = F dt = dp — the impulse-momentum theorem, which is Newton's second law integrated over time. Newton's own statement of the law is in these terms, so this is closer to the Principia than F = ma is.
What this tool implements
- Momentum is a vector. Adding magnitudes without direction is the standard error in collision problems, and one-dimensional sign convention must be stated.
- Momentum is conserved in an isolated system whether or not the collision is elastic; kinetic energy is not. The two conservation questions are kept separate.
- Impulse equals the CHANGE in momentum, so it needs both before and after states, not one.
Sources
- Newton I. Philosophiae Naturalis Principia Mathematica, 1687 — Law II in its original momentum form.
- BIPM, The International System of Units (SI Brochure), 9th edition 2019 — the newton second: https://www.bipm.org/en/publications/si-brochure
What can make this go out of date
- None.
Pick up where you left off
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