ShelfGuides ›
How to calculate unit price for shelf tags
Unit price is the price divided by the amount in the package. It lets shoppers compare a 20 oz bottle with a 2-liter, or a single can with a 12-pack.
The formula
Unit price = price ÷ amount in the package, with the amount in the unit you show on the tag (ounces, fluid ounces, pounds, count…).
- Find the net amount on the package (for example “20 FL OZ (591 mL)”).
- Convert it to the unit you use on the tag, if needed.
- Divide the price by that amount.
- Round for display. This site shows cents to one decimal (12.5¢) under $1, and dollars and cents ($2.66) from $1 up.
Use the same unit for every similar product in the aisle (for example, all soft drinks per fluid ounce), so shoppers can compare.
Worked examples
The prices below are made-up examples to show the math, not real market prices. Each result is exactly what the shelf tag maker prints for the same input.
| Item (example) | Price | Amount | Math | Tag shows |
|---|---|---|---|---|
| Soda, single bottle | $2.49 | 20 fl oz | 2.49 ÷ 20 = $0.1245 | 12.5¢ per fl oz |
| Soda, 2-liter | $3.29 | 2 L = 67.63 fl oz | 3.29 ÷ 67.63 = $0.0486 | 4.9¢ per fl oz |
| Soda, 12-pack cans | $8.99 | 12 × 12 fl oz = 144 fl oz | 8.99 ÷ 144 = $0.0624 | 6.2¢ per fl oz |
| Chips, “2 for $5” | 2/$5 | 9.25 oz each | $5 ÷ 2 = $2.50 each; 2.50 ÷ 9.25 = $0.2703 | 27.0¢ per oz |
| Ground coffee | $5.99 | 2 lb 4 oz = 36 oz | 5.99 ÷ 36 = $0.1664 | 16.6¢ per oz |
| Same coffee, per pound | $5.99 | 2 lb 4 oz = 2.25 lb | 5.99 ÷ 2.25 = $2.662 | $2.66 per lb |
| Pain reliever, 24 count | $6.49 | 24 tablets | 6.49 ÷ 24 = $0.2704 | 27.0¢ per count |
| Milk, 1 gallon | $4.29 | 128 fl oz | 4.29 ÷ 128 = $0.0335 | 3.4¢ per fl oz |
Which is the better buy?
Peanut butter: a 16 oz jar at $3.79 is 23.7¢ per oz (3.79 ÷ 16). A 24 oz jar at $4.99 is 20.8¢ per oz (4.99 ÷ 24). The bigger jar costs more but is cheaper per ounce, and the unit price shows it.
Conversions you will need
| From | To |
|---|---|
| 1 pound (lb) | 16 ounces (oz) |
| 1 gallon | 128 fluid ounces (4 quarts) |
| 1 quart | 32 fluid ounces |
| 1 liter | 33.814 fluid ounces |
| 1 fluid ounce | 29.574 milliliters |
| 1 ounce (weight) | 28.350 grams |
Source: NIST Handbook 44, Appendix C, General Tables of Units of Measurement (PDF on nist.gov).
Common mistakes
- Mixing ounces and fluid ounces. Ounces (oz) measure weight; fluid ounces (fl oz) measure volume. Drinks are labeled in fl oz. Keep similar products in the same unit.
- Forgetting the pack count. A 6-pack of 12 fl oz cans is 72 fl oz, not 12.
- Using the multi-buy total. For “2 for $5”, divide the per-item price ($2.50) by one item’s amount.
- Not updating after a price change. If the price changes, the unit price changes too. Reprint both.
Rules and standards
Unit pricing rules differ by state. These are the official sources we have checked. They are not legal advice; contact your state or local weights and measures office if you are unsure what applies to your store.
- National best practice: NIST Special Publication 1181, Unit Pricing Guide: A Best Practice Approach to Unit Pricing (2025 edition). It is a voluntary guide built on the Uniform Unit Pricing Regulation in NIST Handbook 130, and says it considered the 16 states with current unit pricing regulations. NIST SP 1181 (2025 ed.), doi:10.6028/NIST.SP.1181e2025.
- Ohio, fractions of a cent: Ohio Revised Code 1327.571(B) says that when a posted or labeled price per unit includes a fraction of a cent, the fraction must be prominently displayed, right next to the whole cents, in the same general style, and at least 50% of the height and width of the whole-cent numerals. ORC 1327.571. The shelf tag maker prints the decimal (as in 12.5¢) in the same size and style as the whole cents.
- Ohio, misrepresenting prices: ORC 1327.54 says no person shall misrepresent the price of any commodity sold by weight, measure or count, or represent the price in a way that tends to mislead. ORC 1327.54.
Ready to print? Make shelf tags with unit prices.