Unit Price Calculator
Compare up to three package sizes on price per ounce, litre or item — even in mixed units — and see which is actually cheaper and by how much.
Unit Price Calculator: with the default inputs, best value is Product A — $0.4158 per oz, 4.7% cheaper than Product B..
- Compared per
- per oz (ounces (weight))
- Product A — price per unit
- $0.4158
- Product B — price per unit
- $0.4363
- Product C — price per unit
- —
- Cheaper than the runner-up by
- 4.7%
- Saved on one package of the winner
- $0.25
- Best vs. worst, per unit
- $0.0204
Assumptions
- Quantities are converted through exact definitions (1 lb = 453.59237 g, 1 US gallon = 3.785411784 L) before comparison.
- Weight, volume and count are treated as incomparable without a density — the calculator errors rather than guessing.
- Prices are taken as entered: taxes, deposits, loyalty pricing and coupons are not applied.
- Counted items are assumed identical in size between products, which is often not true.
| Product | Price | Quantity | Price per oz | Rank |
|---|---|---|---|---|
| Product A | $4.99 | 12 oz | $0.4158 | Best value |
| Product B | $3.49 | 8 oz | $0.4363 | Most expensive |
How this is worked out
The formula
Price per unit = price ÷ quantity Quantities are converted to a common base (kilograms for weight, litres for volume, items for count) before comparing, then reported per unit of the first product's measure. Saved on one package = (runner-up price per unit − winner price per unit) × winner's quantity
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Product A — price
- A number.in dollars · 0 or more · defaults to 4.99
- Product A — quantity
- A number.0 or more · defaults to 12
- Product A — measured in
- Choose one of 11 options.ounces (weight) · pounds · grams · kilograms · fluid ounces · cups · quarts · gallons · millilitres · litres · count (each, sheets, pods…)
- Product B — price
- A number.in dollars · 0 or more · defaults to 3.49
- Product B — quantity
- A number.0 or more · defaults to 8
- Product B — measured in
- Choose one of 11 options.ounces (weight) · pounds · grams · kilograms · fluid ounces · cups · quarts · gallons · millilitres · litres · count (each, sheets, pods…)
- Product C — price(under More options)
- Leave the price or quantity at 0 to compare only two.in dollars · 0 or more · defaults to 0
- Product C — quantity(under More options)
- A number.0 or more · defaults to 0
- Product C — measured in(under More options)
- Choose one of 11 options.ounces (weight) · pounds · grams · kilograms · fluid ounces · cups · quarts · gallons · millilitres · litres · count (each, sheets, pods…)
What you get back
- Best valuemain answer
- Compared per
- Product A — price per unit
- Product B — price per unit
- Product C — price per unit
- Cheaper than the runner-up by
- Saved on one package of the winner
- Best vs. worst, per unit
What this assumes
- Quantities are converted through exact definitions (1 lb = 453.59237 g, 1 US gallon = 3.785411784 L) before comparison.
- Weight, volume and count are treated as incomparable without a density — the calculator errors rather than guessing.
- Prices are taken as entered: taxes, deposits, loyalty pricing and coupons are not applied.
- Counted items are assumed identical in size between products, which is often not true.
About this calculator
This is the "which packet is actually cheaper" tool. Shelf labels are supposed to carry a unit price, but they're inconsistent, sometimes wrong, and frequently in a unit nobody uses — one brand per 100 g, the next per pound, the store brand per item. Enter what's on the tags and get a straight answer.
How to use it
Put the price and the quantity from the label into each product. The quantity is the net contents on the package — 12 oz, 1.5 L, 24 count — not the number of servings, which is a marketing number and varies between brands of the same thing.
Units can be mixed within a kind: a 12-ounce jar and a 500-gram jar compare fine, and so do a quart and a two-litre bottle. What you cannot mix is kinds: weight against volume, or either against a count. Peanut butter sold by weight and peanut butter sold by fluid ounce genuinely are not comparable without knowing the density, and the calculator will tell you so rather than quietly making something up.
Results are reported per unit of the first product's measure, so if you entered Product A in ounces, everything comes back per ounce.
What the answer does and doesn't tell you
The unit price is the whole story only when the two products are the same product. A few things that beat a 4% unit-price advantage:
- Waste. The bigger jar is cheaper per ounce and worthless if half of it goes off. This applies to fresh food, opened sauces, anything with a short shelf life, and almost all of what people buy in bulk on impulse.
- Concentration. Concentrated detergent, syrup and cleaner are priced per bottle but used per load or per glass. Compare doses, not volumes.
- Drained weight. Canned goods list net weight including the liquid. The drained weight, when it's given, is the honest number.
- Storage and cash. Two cases of anything you buy today is money you don't have this month, and space you might not have at all.
Reading the results
Best value names the winner and the margin. Saved on one package of the winner answers a more useful question than the percentage does: it's the actual dollars you keep by buying the winner's package instead of the same quantity at the runner-up's rate. If that number is a few cents, the decision doesn't matter — buy the size that fits your life.
Frequently asked questions
▸How do I work out price per ounce?
Divide the price by the number of ounces. A $4.99 jar holding 12 oz is $0.4158 per ounce; an $3.49 jar holding 8 oz is $0.4363. The big jar wins by 4.7%.
▸Can I compare a product sold by weight with one sold by volume?
Not honestly — you'd need the density. Eight fluid ounces of honey weighs about 12 ounces; eight fluid ounces of cereal weighs far less. This calculator refuses the comparison rather than inventing a conversion.
▸Is the bigger size always cheaper per unit?
No. Retailers know shoppers assume it is, and the larger pack is more expensive per unit often enough to be worth checking — particularly on promoted sizes and 'family packs'.
▸Why is the shelf unit price sometimes different from mine?
Stores round, they sometimes use the pre-discount price, and they choose their own basis (per 100 g, per lb, per item). Errors on shelf tags are common enough that checking the arithmetic yourself is worth the ten seconds.
▸What about concentrated products?
Compare uses, not volume. A 40-load bottle at $12 is $0.30 per load; a 25-load bottle at $9 is $0.36 per load, regardless of which bottle holds more liquid. Enter the load count as a 'count' quantity.
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