How to use the unit price calculator
- Enter the price, the size and the unit for each product. Add up to six.
- Choose what to compare: per ounce, per pound, per 100 grams, per liter or per item.
- Read the ranked list. The best value is shown at the top with how much more the others cost.
Formula
Size in base units = quantity x conversion factor (grams, milliliters or items)
Unit price = price / size in the comparison unit
Percent more = (unit price - best unit price) / best unit price x 100
Conversions use exact definitions: 1 oz = 28.349523125 g, 1 lb = 453.59237 g, 1 US fl oz = 29.5735295625 ml and 1 US gallon = 3.785411784 liters.
Worked example: three sizes of cereal
Brand A is $4.49 for 32 oz, which is $0.1403 an ounce. Brand B is $3.19 for 18 oz, which is $0.1772 an ounce. A value pack is $9.99 for 5 lb, which is 80 oz, or $0.1249 an ounce.
The value pack is the best deal, about 11 percent cheaper per ounce than Brand A and about 30 percent cheaper than Brand B, even though the box with the lowest sticker price is Brand B.
When the cheapest unit price is not the best buy
A bigger package is only cheaper if you use it all. Food that spoils, items you do not need or storage you do not have can turn a bargain into waste. Quality, brand and coupons matter too. Use unit price as one input.
Reading shelf labels
Many US stores print a unit price on the shelf tag, but the unit can differ from one product to the next (price per ounce for one, per 100 grams for another). Enter both products here and compare using the same unit.
Assumptions and limits
- Weights, volumes and counts cannot be compared with each other. Mixing them is flagged.
- US customary and metric units are both supported. Fluid ounces are US fluid ounces.
- Taxes, deposits and coupons are not included.
Frequently asked questions
How do I calculate price per ounce?
Divide the price by the number of ounces. $4.49 for 32 ounces is $0.14 an ounce.
Can I compare products in different units?
Yes, if they measure the same thing. A price in pounds can be compared with one in ounces, but not with one in fluid ounces.
What about multipacks?
Multiply the size of one item by the count. A 12-pack of 12 fl oz cans is 144 fl oz.