Grocery Unit Price Comparison Calculator

The Unit Price Trick

Supermarkets love to confuse shoppers with different sizes and pack quantities. The only reliable way to compare products is by price per unit, not price per package.

Unit price = total price / total quantity

The unit can be anything as long as you use the same unit for all items: ounces, grams, count, liters, sheets, etc.

Example 12 oz box for $2.49 → unit price = $2.49 / 12 = $0.2075 per oz 24 oz box for $3.99 → unit price = $3.99 / 24 = $0.1663 per oz The larger box is cheaper per ounce, even though it costs more overall.

Important: Same Unit Required This calculator assumes all items use the same unit of measure. Do not compare ounces with grams without first converting. 1 oz = 28.35 grams.

Bulk Buying Warning Bigger is not always cheaper. Store brands, sales, and package deals sometimes make smaller sizes better value. Bulk buying is only smart if you will actually use the product before it expires.

Savings Percentage The savings % shows how much cheaper the best option is compared to the most expensive. For example, 20% savings means the cheapest option costs 20% less per unit than the most expensive.

Read the shelf tag, then check it Most supermarkets are required to print a unit price on the shelf label, usually in small type under the headline price. It is genuinely useful and it is also where two traps live. The first is that the same category is sometimes labelled in different units, so cereal in one aisle is priced per ounce and the box beside it per 100 grams, which makes them look wildly different when they are not. The second is that promotional tags often show the pre-discount unit price, so the sale item reads as worse value than it is.

Shrinkflation is what this calculator actually catches Manufacturers rarely raise the headline price. They shrink the package instead, from 16 ounces to 14, and leave the price alone. The shelf looks unchanged and the unit price quietly rises 14%. If you keep a note of what you used to pay per ounce for the things you buy every week, this page will tell you when that has happened, which is something the price on the front of the box will never do.

Do the sums before the trip rather than in the aisle, at least for the ten or so items that make up most of a weekly shop. Standing in front of the pasta doing long division is how people end up buying the thing at eye level.