Unit Price Calculator
Compare two packs and see which one is really cheaper.
Good to know. The bigger pack is usually cheaper per unit. Usually. That’s why this exists.
How it works
In plain words
Divide each price by its quantity to get the price of one unit. The lower unit price is the better deal. The percentage shows how much cheaper it is per unit.
The formula
unit price = price ÷ quantity cheaper by = (higher − lower) ÷ higher × 100
Worked example
A is 3.49 for 500 g (0.00698 per gram) and B is 4.99 for 750 g (0.00665 per gram). Option B is cheaper per gram, by about 4.7%.
Sources
No outside data or rates: this is plain arithmetic.
5 automated tests check its answers on every change.
About the unit price calculator
Bigger packs are usually cheaper per unit, but not always. Supermarkets know shoppers assume that, and the "family size" is sometimes the more expensive way to buy. The only way to know is to compare the price of one unit.
To use this calculator, enter the price and quantity of each option in the same unit. Grams against grams, millilitres against millilitres, or sheets against sheets. If one is in kilograms and the other in grams, convert first: 1 kg is 1,000 g.
The "per 100 units" line is handy for comparing against shelf labels, which often show a price per 100 g or 100 ml.
The cheapest unit price is not automatically the best buy. A huge pack is poor value if half of it goes off before you use it, and multi-buy deals only help if you would have bought that much anyway. Think about how much you will actually use, and where you will store it. For things you buy once and use for years, the price per use calculator is a better way to judge value.
Questions people ask
How do I calculate the unit price?
Divide the price by the quantity. 3.49 for 500 g is 0.00698 per gram, or 0.70 per 100 g.
Is the bigger pack always cheaper?
No. It often is, but not always, especially when the smaller pack is on offer. Always compare unit prices.
What if the packs use different units?
Convert them to the same unit first, for example kilograms to grams (× 1,000) or litres to millilitres (× 1,000). The weight and volume converters can help.