Unit rates make comparisons fair: a 750 g box for $4.50 costs $0.006 per gram, a 1 kg box for $5.40 costs $0.0054 per gram, so the bigger box is better value.
How to use the Unit Rate Calculator
- Quantity a (e.g. total price)
- Quantity b (e.g. number of grams)
- Express per how many units of b?
Results update as you type, and everything is calculated in your browser.
How it works
Divide the first quantity by the second. The inverse rate b ÷ a answers the reverse question (how many units of b for one unit of a).
Inputs explained
| Field | What to enter |
|---|---|
| Quantity a (e.g. total price) | A number |
| Quantity b (e.g. number of grams) | A number |
| Express per how many units of b? | A number |
What each result means
- Unit rate a ÷ b = [Quantity a (e.g. total price)]÷[Quantity b (e.g. number of grams)]
- Rate per chosen number of units = [Quantity a (e.g. total price)]÷[Quantity b (e.g. number of grams)]×[Express per how many units of b?]
- Inverse rate b ÷ a = [Quantity b (e.g. number of grams)]÷[Quantity a (e.g. total price)]
Example values
How the main result changes when Quantity a changes and everything else stays at the example values above:
| Quantity a (e.g. total price) | Unit rate a ÷ b |
|---|---|
| 2.25 | 0.003 |
| 3.38 | 0.0045 |
| 4.5 | 0.006 |
| 5.63 | 0.0075 |
| 6.75 | 0.009 |
| 9 | 0.012 |
Formula
Unit rate = a ÷ b (per 1 unit of b)
Worked example
Inputs — Quantity a (e.g. total price): 4.5; Quantity b (e.g. number of grams): 750; Express per how many units of b?: 100.
Results — Unit rate a ÷ b = 0.006; Rate per chosen number of units = 0.6; Inverse rate b ÷ a = 166.66666667.
Key terms
- Rate
- A ratio comparing quantities with different units.
Frequently asked questions
What is a unit rate?
A rate with a denominator of 1, such as $0.006 per gram.
How do I compare prices?
Compute the price per unit for each option; the lower one is better value.
Is speed a unit rate?
Yes – kilometres per one hour.
Why show a rate per 100 units?
Small unit rates are easier to read per 100 g or per 100 km.