Unit price
calculator.
Compare two to four packages by what you pay per ounce, pound, 100 g, fluid ounce, liter, item or square foot. Sizes can be in different units and multipacks are counted properly.
Package B (40 oz for $7.49) is the best value at $0.187 per ounce. Package A costs 11% more per unit.
- Package B (best value)
- $0.187 per ounce
- Package A
- $0.208 per ounce, 11% more
unit price = price ÷ (packs × size); $7.49 ÷ 40 oz = $0.187 per ounceWhich one is
really cheaper?
- Unit price is the price divided by the total quantity: packs × size of each pack.
- Sizes are converted to one unit before comparing, using exact definitions: 1 lb = 453.59237 g, 1 oz = 28.349523125 g, 1 US fl oz = 29.5735295625 mL.
- Weight can only be compared with weight, and volume with volume. Converting between them needs the product's density.
- Unit prices are rounded the way the NIST unit pricing regulation sets out: to the cent at $1 or more, and to the tenth of a cent below $1.
How do you calculate unit price?
Divide the price by the quantity. A 24-ounce box for $4.99 costs 4.99 ÷ 24 = $0.208 per ounce. A 40-ounce box for $7.49 costs 7.49 ÷ 40 = $0.187 per ounce, so the larger box is cheaper per ounce, by about 11%.
For a multipack, multiply first: a 6-pack of 12 fl oz cans holds 72 fl oz. For “3 for $10”, enter $10 and 3 packs.
unit price = price ÷ (number of packs × size of each pack)How do you compare packages in different units?
Convert both sizes to the same unit first. A 1 kg bag is 1000 g. A 2 lb bag is 2 × 453.59237 = 907.18 g. At $3.20 and $2.99, the kilogram bag costs $0.0032 per gram and the 2 lb bag $0.0033 per gram, so the kilogram bag is about 3% cheaper even though its price tag is higher. The calculator does this conversion for you and can show the result per ounce, per pound, per 100 g or per kilogram.
1 lb = 453.59237 g 1 oz = 28.349523125 g
1 US fl oz = 29.5735295625 mL 1 US gal = 3.785411784 LIs the bigger package always the better deal?
No. Bulk packages are often cheaper per unit, but not always: sale prices, coupons and multipack deals on smaller sizes regularly beat the large size. Compare the unit price each time. A lower unit price is only a saving if you use the product before it spoils or expires, and if you have the space to store it.
Why do shelf labels show different units?
In the U.S., stores that show unit prices follow state rules, most of them based on the NIST Uniform Unit Pricing Regulation. It asks stores to price every size of the same product in one consistent unit: per ounce, pound, 100 g or kilogram for weight, per fluid ounce, quart, gallon, liter or 100 mL for liquids, and per item for counts. In practice, labels still mix units, for example soda priced per fluid ounce in cans and per liter in bottles. Enter the package sizes here to compare them on one basis.
NIST’s guide also says “loads,” “uses” and “servings” are not acceptable units of measure. A detergent that claims more loads is not necessarily more product, so compare it by weight or volume.
Worked examples.
Small box or big box
Cereal: 24 oz for $4.99, or 40 oz for $7.49.
The 40 oz box is the better value at $0.187 per ounce. The 24 oz box costs 11% more per ounce ($0.208).
Load this exampleA multipack against a bottle
A 6-pack of 12 fl oz cans for $5.49, or a 2-liter bottle for $2.29.
The bottle costs $0.034 per fl oz; the cans cost $0.076, more than twice as much (125% more).
Load this exampleKilograms against pounds
Rice: a 1 kg bag for $3.20, or a 2 lb bag for $2.99.
The 1 kg bag is cheaper: $0.091 per ounce against $0.093 for the 2 lb bag, which costs 3.0% more per ounce.
Load this examplePaper towels by the sheet
6 rolls of 110 sheets for $8.99, or 8 rolls of 140 sheets for $15.49.
The 6-roll pack is slightly cheaper: $1.36 per 100 sheets against $1.38 (1.5% more).
Load this exampleWhat this calculator
does not do.
- It compares price per quantity only. Quality, brand, waste and how fast you use the product are up to you.
- Weight and volume cannot be compared directly. To compare 1 lb of flour with a 4-cup bag, convert one of them with the cooking converter first.
- Prices are compared as entered. Include coupons or deals in the price, and leave sales tax out (or include it for every package).
Common questions.
How do I calculate price per ounce?
Divide the price by the number of ounces. $3.99 for 16 oz is 3.99 ÷ 16 = $0.249 per ounce.
How do I calculate price per pound from ounces?
Divide the price by the ounces, then multiply by 16. $3.99 for 12 oz is $0.3325 per ounce, or $5.32 per pound.
How do I compare “2 for $5” with a single item?
Enter $5 as the price and 2 as the number of packs. The calculator divides by the total quantity of both packs.
Should I compare fluid ounces with ounces?
Only for water-like liquids. A fluid ounce is a volume (29.57 mL) and an ounce is a weight (28.35 g). Choose fluid ounces for drinks and ounces for solids, as printed on the package.
- NIST Handbook 130 (2026), IV.C Uniform Unit Pricing Regulation — units for unit prices and rounding to the cent or tenth of a cent
- NIST SP 1181-2025, Unit Pricing Guide: A Best Practice Approach — recommended units; loads, uses and servings are not units of measure
- NIST Handbook 44 (2026), Appendix C: General Tables of Units of Measurement — exact pound, ounce, gallon and inch definitions
Every size is converted to grams, milliliters, items, meters or square meters with exact unit definitions, then divided into the price. Our tests check hand-calculated comparisons, cross-unit invariants (the same product in grams, kilograms, ounces and pounds must give one unit price), multipacks, ties and mismatched units.
Built and reviewed by CalculatorLab against the sources above; every worked example on this page is re-checked by our automated test suite before each release. How we build and check calculators. Found a problem? Tell us.