Unit price calculator
Which size is the better buy? Enter the price and net quantity of two to four products – the calculator converts them to the same unit, finds the cheapest price per ounce (or per kg, liter, 100 g or item) and shows how much you save in percent.
How it is calculated
Unit price formula
Unit price = price ÷ quantity, with every product converted to the same unit first. A 12 oz box for $3.49 costs 3.49 ÷ 12 = $0.291 per ounce. A 1 lb bag is 16 oz, so $4.29 ÷ 16 = $0.268 per ounce.
Example: three sizes compared
| Product | Price | Size | Unit price | more than the best deal |
|---|---|---|---|---|
| A | $3.49 | 12 oz | $0.291 / oz | +35.95% |
| B | $4.29 | 1 lb | $0.268 / oz | +25.33% |
| C | $5.99 | 28 oz | $0.214 / oz | best deal |
The 28 oz size wins. Compared with the 12 oz box you save 1 − 0.2139 ÷ 0.2908 = 26.44% per ounce. The last column works the other way round: the 12 oz box costs 35.95% more per ounce than the 28 oz size. Both numbers are correct – they just use a different base.
Which units do stores use?
In the US, the model rule is the Uniform Unit Pricing Regulation in NIST Handbook 130, adopted by the NCWM (National Council on Weights and Measures) for jurisdictions that choose to use it. It applies when a store provides unit prices and says (Section 2) that the unit price must be shown per kilogram or 100 g, or per pound or ounce, for products labeled by weight; per liter or 100 mL, or per gallon, quart, pint or fluid ounce, for liquids; and per item for products sold by count – and uniformly for all package sizes of a product. That is exactly what this calculator does for you.
Conversions used: 1 lb = 16 oz = 453.59237 g, 1 fl oz (US) = 29.5735 mL (NIST SP 811). Ounces (weight) and fluid ounces (volume) are different units and cannot be compared without the product’s density.
Tips
- Multipacks: enter the total quantity (6 × 16.9 fl oz = 101.4 fl oz).
- Items like eggs, diapers or dishwasher pods: compare by count.
- Bigger isn’t always cheaper – a sale on a small size often beats the family pack.
Frequently asked questions
How do you calculate unit price?
Divide the price by the quantity in the same unit. $5.99 for 28 oz: 5.99 ÷ 28 = $0.214 per ounce. For a price per pound, multiply the price per ounce by 16.
How do I compare ounces and pounds?
Convert to one unit first: 1 lb = 16 oz. A 1 lb bag for $4.29 is $4.29 ÷ 16 = $0.268 per ounce, which you can compare directly with a 12 oz box at $0.291 per ounce.
Can I compare ounces with fluid ounces?
No. Ounces measure weight, fluid ounces measure volume. Without the density of the product the two can’t be converted, so enter all sizes the way they are labeled on the package.
Why is the savings percentage smaller than the price difference?
The base is different. The 28 oz size is 26.44% cheaper per ounce than the 12 oz box, but the 12 oz box is 35.95% more expensive than the 28 oz size. Savings use the higher price as the base, the markup uses the lower one.
How do I calculate unit price in Excel?
With the price in A2 and the quantity in B2: =A2/B2. For a pound bag compared per ounce: =A2/(B2*16). The best deal in a column: =MIN(C2:C5).
Sources and legal basis
- HB 130 IV.C Sec. 2: NIST Handbook 130 (2026), Uniform Unit Pricing Regulation – terms for unit pricing
- NIST SP 811, Appendix B.9 – conversion factors (ounce, pound, fluid ounce)
As of:
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