About the Unit Price Calculator
Bigger packs are not always cheaper per ounce. This unit price calculator compares up to three products by their price per unit so you can see which one is really the better deal. Enter each item’s price and size, choose the unit, and it converts everything to the unit of the first item and names the winner.
Use it in the grocery aisle, when comparing bulk-store packs with regular sizes, or when a sale price on a small pack competes with an everyday price on a large one. It handles mixed units within the same family — for example a 1 lb bag against a 32 oz bag, or a 2 L bottle against a 12 × 12 fl oz pack entered as 144 fl oz.
Weights can only be compared with weights, volumes with volumes and counts with counts. Leave the third item’s price at 0 to compare just two — its result line is then hidden. Conversions use the exact US customary definitions published by NIST, and fluid ounces, quarts and gallons are US (not UK imperial) measures.
How to use the unit price calculator
- 1Enter the price and size of the first product and choose its unit.
- 2Enter the second product (and a third if you like).
- 3Use any unit of the same kind — pounds against ounces works, pounds against liters does not.
- 4Read the best deal and each item’s price per unit.
Formula and method
Each package size is converted into the unit of item A using exact conversion factors (1 lb = 16 oz = 453.59237 g, 1 US fl oz = 29.5735 mL, 1 US quart = 946.353 mL, 1 US gallon = 3.785411784 L, per NIST Handbook 44). The price is then divided by that converted quantity to give a price per unit, and the item with the lowest unit price is the best value.
The percentage shown compares the cheapest unit price with the most expensive one. It does not account for waste — a bigger pack is only a better deal if you will use it before it spoils.
- Price
- Shelf price of the package
- Size
- Net quantity printed on the package
Worked examples
12 oz for $4.99 vs 20 oz for $7.49
Item A costs about $0.416 per ounce and item B about $0.375. The larger pack is roughly 9.9% cheaper per ounce.
1 lb for $3.49 vs 32 oz for $5.99
32 oz is 2 lb, so item B costs $2.995 per pound against $3.49 for item A — about 14.2% cheaper per pound.
Three pack sizes by count
Per item, the 24-pack is $0.541, the 40-pack $0.500 and the 10-pack $0.549. The 40-pack wins and is about 9% cheaper per item than the small pack.
Frequently asked questions
How do you calculate unit price?+
Divide the price by the quantity. A $4.99 box holding 12 ounces costs 4.99 ÷ 12 = $0.416 per ounce. Compare that number across products instead of comparing sticker prices.
Is buying in bulk always cheaper?+
No. Larger sizes are often cheaper per unit, but sales on smaller sizes, store brands and coupons frequently reverse that. Always compare the unit price, and remember bulk only saves money if you use it all.
Why does the shelf tag show a different unit price?+
Stores may use a different unit (per 100 g or per quart), and some calculate it from the regular price rather than the sale price. Entering the actual price you will pay gives the true comparison.
Can I compare ounces with fluid ounces?+
Not directly. Ounces measure weight and fluid ounces measure volume; converting between them requires the product’s density. Compare liquids in fluid ounces, milliliters or liters and solids by weight.
How do I compare multipacks?+
Multiply the count by the size of each unit. A 12-pack of 12 fl oz cans is 144 fl oz; a 6-pack of 16.9 fl oz bottles is 101.4 fl oz. Enter those totals as the size.