What a unit price is and why it helps
A unit price is the price of one standard unit of a product: one ounce, one pound, one liter, 100 grams, one roll or one load of laundry. You get it by dividing the price you pay by the amount you get. A $2.99 jar that holds 12 ounces costs about 24.9 cents per ounce. The shelf price alone does not show which package gives you more for your money. The unit price puts different sizes and brands on the same scale.
How to use this calculator
Enter the price of each item, the number of packages that price covers, the size printed on each package and its unit. You can mix U.S. and metric units: the calculator converts every item to one base unit before it divides. If you have a coupon, enter the percent off, the dollars off or both. The percent comes off first, then the dollars. You can compare two items or add up to six. The result ranks them from cheapest to most expensive per unit and shows how much less the best buy costs than the most expensive item. You can show weight per ounce, pound, 100 g or kg, and liquids per fluid ounce, gallon, 100 mL or liter.
A worked example
Suppose you compare three bags of rice: $2.99 for 12 oz, $5.60 for 20 oz and $7.49 for 1 kg. One kilogram is about 35.27 ounces (exactly 1,000 ÷ 28.349523125). The unit prices are about 24.9 cents per ounce for the first bag, 28 cents for the second and 21.2 cents for the third. The 1 kg bag is the best buy and costs about 24.2% less per ounce than the 20 oz bag, which is the most expensive per ounce even though it is bigger than the 12 oz bag. With a 25% coupon the 20 oz bag costs $4.20, or about 21.0 cents per ounce, and becomes the best buy.
Bigger is not always cheaper
Large packages often cost less per unit, but not always. Sales, store brands, coupons and small packs on special can beat the big pack. A lower unit price also only saves money if you use everything before it spoils or expires.
How unit price labels work in U.S. stores
Many supermarkets print a unit price on the shelf tag. The rules come from the states, not from one national law. The National Institute of Standards and Technology (NIST) publishes a model rule, the Uniform Unit Pricing Regulation in NIST Handbook 130, which states can adopt, change or leave out, so whether a store must show unit prices depends on where you shop. The model rule applies to a store that provides unit prices, and it says how:
- A product has the same unit for every package size the store sells: per ounce, pound, 100 g or kilogram for weight, per fluid ounce, pint, quart, gallon, 100 mL or liter for liquids, and per item for count.
- Packages under 1 oz or 1 fl oz (about 28 g or 29 mL), products with a total price of 50 cents or less, and products sold in only one brand and size are exempt.
- A unit price of a dollar or more is shown to the nearest cent. Under a dollar, a store uses tenths of a cent or whole cents, but not both.
NIST also publishes a voluntary guide for retailers, NIST SP 1181, and your state weights and measures office can tell you the local rule. When two shelf tags use different units (one per ounce, the other per pound), convert both to the same unit first, which this calculator does for you. For other conversions, use the U.S. unit converter. To work out the price after a percent-off sale, use the discount calculator.
What this calculator leaves out
It compares price per unit only, not sales tax, deposits, shipping, price per serving, quality or how much you will really use. Weight, volume, count, sheets and loads are ranked separately, because an ounce of weight is not a fluid ounce, and sheets or loads cannot be turned into ounces. The unit price on a store tag may be rounded differently.
Frequently asked questions
How do I calculate the unit price of a product?
Divide the total price by the total amount. For $4.80 for 24 oz, 4.80 ÷ 24 is $0.20 per ounce. For a multipack, multiply the number of packages by the size of each one first: $6.00 for 6 cans of 12 fl oz is $6.00 ÷ 72 fl oz, or about 8.3 cents per fluid ounce.
Is the bigger package always the better deal?
No. Bigger packages are often cheaper per unit, but a sale, a coupon or a store brand can make a smaller package cheaper. Compare unit prices, not package sizes.
Can I compare ounces with fluid ounces?
No. An ounce (oz) measures weight and a fluid ounce (fl oz) measures volume, and they are not the same thing. You cannot compare a product sold by weight with one sold by volume unless you know its density, so this calculator ranks them separately.
Official sources
Checked on October 16, 2026: NIST Handbook 130, 2026 edition, Uniform Unit Pricing Regulation (section IV.C), NIST SP 1181, Unit Pricing Guide (2025 edition) and NIST SP 811, conversion factors.
General information and arithmetic, not shopping, financial or legal advice. Rules and prices differ by state and store.