The Unit Price Calculator answers the everyday grocery question 'which one is actually cheaper?' when two products come in different sizes. It converts every option to the same unit — per ounce, per 100g, per item — divides price by amount, and ranks them so the real best value is obvious instead of guessed.

How the Unit Price Calculator works

Unit price is just price divided by amount, but the work is in making the amounts comparable. A 1.5 L bottle and a 500 mL bottle can't be compared until both are in the same unit. The calculator converts each product's size into a base amount — grams for weight, millilitres for volume, a simple count for items — using exact factors (1 lb = 453.592 g, 1 kg = 1,000 g, 1 L = 1,000 mL, 1 fl oz = 29.5735 mL), multiplies by the pack count, subtracts any coupon from the price, and then divides. The product with the lowest result is the best value.

Inputs and what they mean

Each product takes a price, a size, and a unit. The pack count handles multipacks — enter the size of one unit and how many are in the package. The optional coupon is a dollar amount taken off the price before dividing, so the unit price reflects what you'll pay at the register. The compare unit at the top decides what everything is normalized to; switch it between per ounce, per 100g, per litre, and per item depending on the product. Tiny unit prices are shown to three or four decimal places so a difference of a few tenths of a cent per ounce is still visible.

Limits and edge cases

You can only compare within one unit family. Weight (oz, lb, g, kg), volume (mL, L, fl oz), and count (ct) are separate — a fluid ounce of liquid is a volume, not a weight, and comparing it to a per-ounce weight is meaningless. When your products span families the calculator warns you and ranks only the ones matching the compare unit. The calculator also assumes the products are equivalent in quality and that you'll use all of what you buy — a lower unit price isn't a saving if the larger size spoils before you finish it. For perishables, factor in waste; for items you'll consume fully, unit price is the cleanest cost comparison there is.