Unit Rate Calculator
Reduce a rate to "per one" — and compare two package sizes to see which is actually cheaper.
A unit rate expresses a ratio with a denominator of one: 3 for 7.
How the unit rate calculator works
A unit rate expresses a ratio with a denominator of one: 3 for 7.50 is 2.50 each; 240 km in 3 hours is 80 km/h. Reducing to "per one" is what makes two quantities comparable when they come in different sizes.
The supermarket case is the useful one. A bigger pack is usually but not always cheaper per unit, and shelf labels round the unit price enough to hide small differences. Entering both packs here shows which wins and by how much.
Formula: unit rate = quantity ÷ amount
Worked examples
| Inputs | Option A per unit | Note |
|---|---|---|
| 3 for 7.50 against 5 for 11.40 | 2.5 | 2.50 vs 2.28 — B wins |
| 240 km in 3 hours | 80 | 80 km/h |
| The bigger pack is not always cheaper | 2 | 2.00 vs 2.17 — A wins |
FAQFrequently asked questions
What is a unit rate?
A ratio reduced so the second quantity is one: 2.50 each, 80 km per hour, 12 g per serve.
How do I find the unit price?
Divide the price by the quantity. 7.50 for 3 is 2.50 each.
Is the bigger pack always cheaper per unit?
No. It usually is, but promotions on small packs regularly beat the large size — which is what this comparison is for.
Why do shelf unit prices sometimes disagree?
They round, and they may use a different base unit (per 100 g rather than per kg), so two labels can look inconsistent while both being right.
What is the inverse rate?
How many units you get per one of the amount — 0.4 items per dollar, the same information the other way up.
Where these figures come from
- NIST Digital Library of Mathematical Functions — reference definitions for elementary and special functions
- Wolfram MathWorld — definitions and formulas for every topic on this page
- NIST/SEMATECH e-Handbook of Statistical Methods — the statistical formulas (mean, variance, z, confidence intervals, sample size)
- Australian Curriculum (ACARA) — Mathematics — the terms and methods taught in Australian schools
Last checked: September 2026. Formulas are fixed by mathematics and do not change with tax years or regulations.