How to use the Unit Price Calculator
- Enter the price and the quantity of product A.
- Enter the price and the quantity of product B, in the same unit as A.
- Read the better deal and the price per unit of each.
- Check the saving per unit, then think about whether you will actually use the larger amount.
Formula used
Unit price = price ÷ quantity. The product with the lower unit price is the cheaper per unit. Saving = (higher − lower) ÷ higher × 100.
Worked example
Here is the Unit Price Calculator worked through with the example values shown above, so you can check each step by hand.
| Inputs | |
|---|---|
| Product A: price | $4.5 |
| Product A: quantity | 500 |
| Product B: price | $8 |
| Product B: quantity (same unit as A) | 1,000 |
| Result | |
| Better deal | Product B |
| Price per unit, product A | 0.009 |
| Price per unit, product B | 0.008 |
| Saving per unit with the better deal | 11.11% |
How to compare
Divide the price by the quantity to get the unit price. Product A costs $4.50 for 500 g, which is 0.009 per gram. Product B costs $8.00 for 1,000 g, which is 0.008 per gram. B is cheaper per gram, by 11.1%, so B is the better deal.
Small unit prices are easier to read per 100 g or per kg: A is $9.00 per kg and B is $8.00 per kg.
Make the units match
The calculation only works when both quantities use the same unit. If one product is in kilograms and the other in grams, convert one first: 1 kg is 1,000 g. The same goes for litres and millilitres, or ounces and pounds. The converters on this site help, such as the weight converter and the volume converter.
For products sold by count, such as 12 rolls versus 18 rolls, use the count as the quantity. For items that differ in size per piece, such as toilet paper with different sheet counts, compare per sheet instead.
When the cheaper unit price is not the better buy
Buying more only saves money if you use all of it. Fresh food that spoils, a product that expires before you finish it, or a pack that is too big to store can cost more than a smaller one. Quality and ingredients also differ: a cheaper product may not be equivalent.
Watch for shrinking packs, sale prices that apply only to one size, and loyalty discounts. Enter the actual price you will pay, after any discount.
Using it in the shop
Many shops show a unit price on the shelf label, but not always in the same unit for different brands, which is why a quick calculation is useful. Compare the price per kilogram or litre, then decide.
The discount calculator on this site shows the price after a percentage off, which you can then enter here for the sale price.
Frequently asked questions
Do both products need the same unit?
Yes. Convert one of them first, for example 1 kg is 1,000 g, so both quantities use grams.
Is the cheaper unit price always the better buy?
Not if you cannot use it all before it spoils or if quality differs. Compare what you will really use.
What is a unit price?
The price for one unit of measure, such as per gram, per litre or per item.
How do I compare more than two products?
Compare two at a time and keep the winner, or calculate each unit price separately and pick the lowest.
Does it work in any currency?
Yes. Use the currency selector to change the symbol. The comparison is the same.
What if the prices are equal per unit?
The calculator says the unit prices are the same, and you can choose by quantity or quality.
This calculator gives estimates for information only. Actual figures from a bank, employer, tax authority or doctor may differ. It is not financial, tax, legal or medical advice.