Formula
Unit price = price ÷ sizeSaving = (higher unit price − lower unit price) ÷ higher unit price How it works
Shelf prices hide the real cost of a product because package sizes differ. Dividing each price by its size puts both on the same footing — dollars per ounce, per gram, per sheet or per item — so the cheaper one is obvious.
Enter both sizes in the same unit. If one jar is in grams and the other in ounces, convert first (1 oz = 28.35 g). For multipacks, use the total quantity, such as 12 cans × 12 fl oz = 144 fl oz.
A lower unit price is only a better deal if you will use it all. Bulk packs of perishables, or a sale on a size you would not normally buy, can cost more in the end if some goes to waste.
Frequently asked questions
Is the bigger package always cheaper per unit?
Often, but not always. Sales and coupons on smaller sizes regularly beat the bulk price, which is why it pays to check the unit price every time.
What does “Package B price that would match A” mean?
It is what package B would have to cost to have exactly the same unit price as package A — a handy break-even figure when one item is on sale.