Unit price calculator

How unit price works

Unit price is the price divided by the amount you get. A 12 oz bag of coffee at $9.00 is 75 cents an ounce. A 3 lb bag at $17.99 is 48 ounces, so about 37 cents an ounce. The bigger bag costs twice as much up front and about half as much for each cup.

The calculator turns every size into the same base unit first (ounces for weight, fluid ounces for liquids, items for counts), so you can compare a bag in grams with one in pounds.

Weight and volume are not the same ounce

“Oz” on a bag of rice is weight. “Fl oz” on a bottle of oil is volume. They only line up for water and things close to it, so the calculator won't compare one with the other. If a shelf tag uses a different unit from the package, use the one printed on the package.

When the bigger pack isn't the better buy

• You won't finish it. Food that goes off before you use it costs more than it saved.
• The smaller size is on sale. Sales often go on the size people buy most, so check every time rather than assuming.
• The store brand in a small size beats the name brand in a big one. Compare across brands, not just sizes.
• Multi-buy offers (“2 for $5”) sometimes price each item the same as buying one. Work out the price of one.

Shelf tags can be wrong, too

Most US stores print a unit price on the shelf tag, but stores don't always use the same unit for two sizes of the same product (per ounce on one, per pound on the other). Typing both into a calculator takes a few seconds and settles it.

For keeping track of what you pay over time, see how to keep a grocery price book.