How to compare unit prices
Divide each price by its size to get the cost per unit, using the same unit for both. Shelf tags often do this for you, but stores sometimes switch units between products, show per-count on one and per-ounce on another, or leave sale prices out.
Example: a 12 oz jar for $3.49 is $3.49 ÷ 12 = $0.2908 an ounce. A 32 oz jar for $7.99 is $0.2497 an ounce, so the big jar is 14.1% cheaper per ounce. The calculator converts units for you, so you can compare 500 g against 1.5 lb or 1 L against 32 fl oz.
When the bigger size isn't the better deal
- Sales on smaller sizes often beat the bulk price. Always check.
- Waste: if you'll throw out a third of a big container, the real unit price is 50% higher.
- Coupons are a fixed amount off, so they cut the unit price more on smaller sizes.
- Shrinkflation: sizes quietly change. Compare by unit price, not package.
Working out a sale price? Use the discount calculator, then add tax with the sales tax calculator.
Frequently asked questions
How do you calculate the unit price?
Divide the price by the quantity: $4.50 for 18 oz is $0.25 an ounce. Use the same unit for every product you compare.
Is buying in bulk always cheaper?
Usually, but not always. Sales, coupons and store brands often make smaller sizes cheaper per unit, and bulk only saves money if you use it all.
Can I compare ounces with grams?
Yes. Choose each product's own unit, and the calculator converts them, showing all prices in the first product's unit. Weight and volume can't be compared directly, though.
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