Unit Price Calculator

How unit price is calculated

Unit price = Price ÷ Quantity (in a common unit)

Products are converted to a common unit first, so you can compare a 500 g pack with a 1 kg pack, or a 16 oz jar with a 500 g jar. Weights are compared per kilogram, volumes per liter and counted items per item, and the result also shows the per-100 g or per-100 mL price that many shelf labels use.

Worked example

Product A costs 3.49 for 500 g; product B costs 5.99 for 1 kg.

• A: 3.49 ÷ 0.5 kg = 6.98 per kg (0.698 per 100 g)
• B: 5.99 ÷ 1 kg = 5.99 per kg (0.599 per 100 g)

B is cheaper per kilogram. A costs (6.98 − 5.99) ÷ 5.99 ≈ 16.5% more for the same amount.

Things a unit price does not tell you

• Waste. A bigger pack only saves money if you use it before it spoils.
• Quality and concentration. A concentrated detergent may do more washes per liter than a cheaper, diluted one. Compare price per wash or per serving when the packaging states it.
• Weight versus volume. You cannot compare a product sold by weight with one sold by volume without knowing its density, so the calculator asks you to compare like with like.

US and UK fluid ounces are different

A US fluid ounce is 29.5735295625 mL; a UK (imperial) fluid ounce is 28.4130625 mL, about 4% smaller. Choose the one printed on the label. Weight ounces (oz) are the same in both countries: 28.349523125 g.

Common questions

Do shops have to show unit prices?

Rules differ by country. The European Union, for example, requires most products to show a price per unit of quantity, and many US states have their own unit-pricing rules. Where a shelf label shows a unit price, check that the two products use the same unit before comparing.

What about multipacks and "buy one get one free"?

Enter the price you actually pay and the total quantity you receive. Two 400 g packs for 5.00 is 5.00 for 800 g.