What is unit price?
Unit price is the cost of one unit, such as one item, one gram, one kilogram, one millilitre or one litre.
Unit price is the price for one standard unit of something. It helps you compare two products that come in different pack sizes, weights, volumes or quantities.
For example, if a 1kg bag of rice costs £5, the unit price is £5 per kg. If a 500g bag costs £3, the unit price is £6 per kg, so the larger bag is cheaper per kilogram.
Why unit price matters
Unit price matters because the lowest pack price is not always the best deal. A smaller item can look cheaper at the till while costing more per gram, litre or item.
Unit price formula
The basic unit price formula is simple: divide the total price by the total quantity.
Unit price = total price ÷ total quantityIf the units are different, convert them first. For example, compare grams with grams or litres with litres, not grams with kilograms unless you convert one of them.
Comparing two products?
Use the unit price comparison calculator to compare two pack sizes or offers on the same unit basis.
Unit price example
Suppose one product costs £3 for 500g and another costs £5 for 1kg.
| Product | Calculation | Unit price |
|---|---|---|
| Product A | £3 ÷ 500g | 0.6p per gram, or £6 per kg |
| Product B | £5 ÷ 1,000g | 0.5p per gram, or £5 per kg |
| Result | Compare the same unit | Product B is cheaper per kg |
Unit price and discounts
A discount can change the unit price, but only if you apply it to the actual price you will pay. If one product has a 20% discount and another has no discount, compare the discounted unit price against the normal unit price of the other item.
Discounted unit price = discounted price ÷ quantityThis is useful when comparing supermarket offers, multipacks, refills and “bigger pack” deals.
Compare like-for-like units
The most common mistake is comparing different units without converting them first. A price per 100g should be compared with another price per 100g. A price per litre should be compared with another price per litre.
- Use grams or kilograms for weight.
- Use millilitres or litres for liquids.
- Use price per item for packs of identical items.
- Use the final price after discounts if the offer is applied at checkout.
Common uses of unit price
- Comparing grocery pack sizes.
- Checking whether a multipack is better value.
- Comparing sale prices against normal prices.
- Working out price per serving.
- Comparing household products such as washing liquid, paper rolls or toiletries.
Unit price FAQs
What does unit price mean?
Unit price means the cost of one standard unit, such as one item, one gram, one kilogram, one millilitre or one litre.
How do you calculate unit price?
Divide the total price by the total quantity. For example, £5 for 1kg is £5 per kg.
Why is unit price useful?
It helps you compare products that come in different sizes. The item with the lowest headline price is not always the cheapest per unit.
Should I compare unit price before or after a discount?
Use the final price you will actually pay after the discount, then divide it by the quantity.