The unit price is the price divided by the size, such as the cost per ounce or per liter. It shows which package is cheaper for the same amount, even when sizes and units differ. Enter two or more items and this calculator converts them to one unit, ranks them and shows how much more each costs than the best value.
A worked example
These hypothetical rice prices are US dollars, not current store offers. Assume the same product quality and usable quantity.
Three bags of the same rice: a 24 oz bag for 4.29, a 2 lb bag for 5.49 and a 1 kg bag for 6.99. Converted to ounces, the 2 lb bag costs about 0.172 per ounce, the 24 oz bag about 0.179 and the 1 kg bag about 0.198. The 2 lb bag is the best value; the 24 oz bag costs 4.2% more per ounce and the 1 kg bag 15.5% more.
Why shelf labels can mislead
Stores sometimes show unit prices in different units for similar products, for example per ounce on one item and per pound on another, which makes quick comparison hard. The National Institute of Standards and Technology unit pricing guide sets out how unit prices should be shown consistently. This calculator converts everything to one unit for you, using exact conversion factors such as 1 lb = 16 oz and 1 kg ≈ 35.27 oz.
When the cheapest unit price is not the best buy
A larger pack only saves money if you use it before it spoils and can afford it without taking money from another need this week. Compare items of similar quality, and include any coupon or member price in the price you enter. Weight and volume cannot be compared directly, so the calculator asks you to compare items measured the same way.
Enter all prices in the same currency; Display currency changes labels only, not exchange rates. Fluid ounce, quart and gallon options are US measures, not Imperial measures. A product’s weight cannot be converted to its volume without its density, which this tool does not estimate. Include any applicable charges consistently in the prices you compare. This is an educational price comparison, not a recommendation to buy a product.
Putting the savings to use
Small savings on regular purchases add up over a year. Track your grocery line in the monthly budget template, and see the yearly effect of repeating costs with the subscription and habit cost calculator.