Home › Shopping › Price Per Unit Calculator
Price Per Unit Calculator
Two sizes of the same product, two different prices — which is actually cheaper? Enter both items below and this calculator works out the price per ounce, per pound, per litre or per item, and tells you which deal wins and by how much.
Prices are compared as entered, before tax. Unit prices are estimates rounded for shelf comparison; check the store's own unit-price tag when it is printed.
How it works
Each item is reduced to a price per single base unit. Weight is converted to ounces (1 lb = 16 oz, 1 kg = 35.274 oz, 1 g = 0.035274 oz) and volume to fluid ounces (1 cup = 8 fl oz, 1 L = 33.814 fl oz, 1 ml = 0.033814 fl oz); counted items use price per item. Then unit price = price ÷ size in base units, and the cheaper unit price wins; the saving is (higher − lower) ÷ higher × 100%. Worked example: Item A at $4.99 for 24 oz costs $4.99 ÷ 24 = $0.208 per oz ($3.33 per lb). Item B at $3.49 for 16 oz costs $3.49 ÷ 16 = $0.218 per oz ($3.49 per lb). Item A is cheaper by about ($0.218 − $0.208) ÷ $0.218 = 4.7%, even though its shelf price is higher — the bigger pack wins here.
Frequently asked questions
Why is the bigger pack not always cheaper per unit?
Because manufacturers price sizes independently — a jumbo pack can carry a premium for convenience, and a small pack can be on sale. Only the per-unit price tells the truth, which is why stores print it on the shelf tag.
Can I compare a weight item with a liquid item?
No — ounces of weight and fluid ounces measure different things, so the calculator shows each unit price separately and declines to name a winner. Compare dry goods with dry goods and liquids with liquids.
What about count items, like eggs or trash bags?
Use the Items (count) unit: enter the number of items in the pack and you get the price per egg, per bag, and so on. A 12-pack at $4.20 is $0.35 per egg; an 18-pack at $5.85 is $0.325 per egg.
Should I trust the store's shelf unit price instead?
Usually yes, but shelf tags can be wrong or missing, and they rarely let you compare two different unit systems (say, per ounce vs per pound). This tool does the conversion for you.
Does this include tax or coupons?
No — it compares shelf prices as entered. If you have a coupon for one item, subtract it from that item's price first, then compare.