Unit price calculator
Which package is the better deal? The one with the lowest unit price: its price divided by how much is in it. Enter two to six packages below, in any mix of ounces, pounds, grams and kilograms (or fluid ounces, milliliters and liters, or a count), and the calculator ranks them cheapest per unit first, shows how much more each of the others costs per unit, and what that difference adds up to.
Nothing you type leaves your browser. The address bar updates as you type, so you can bookmark or share a comparison. Packs is the number of items in a multipack (2 for 2 × 12 oz); leave it blank for 1. Volumes are US measures (US fl oz, cups, pints, quarts, gallons).
The shrinkflation check
A smaller “new” pack at the same shelf price shows up here as a higher unit price. Put last year’s pack and this year’s side by side: if the old one wins, you are paying more for less. For a single before-and-after change use the shrinkflation calculator, see the worst hidden price hikes we have on record, and if you catch a pack that shrank, submit a sighting.
Real examples: old pack vs new pack
Sizes and shelf prices as recorded by the source of each documented case. Unit prices are ours, worked out from those numbers.
| Product | Old · new pack | Unit price | Change |
|---|---|---|---|
| Kellogg's Coco Pops (Australia) 🇦🇺 Source: theaustralian.com.au | Oct 2021: 650 g, A$7.50 Oct 2026: 535 g, A$9.00 | A$1.15 → A$1.68 per 100 g | +45.8% Compare these |
| Cadbury Roses tub (UK, Christmas 2026) 🇬🇧 Source: thegrocer.co.uk | 2025: 550 g, £7.00 2026: 475 g, £7.00 | £1.27 → £1.47 per 100 g | +15.8% Compare these |
| Folgers classic roast ground coffee 🇺🇸 Source: lendingtree.com | 2019/20: 48 oz, $9.96 2024: 40.3 oz, $14.87 | $0.208 → $0.369 per oz | +77.8% Compare these |
Worked example
Illustrative numbers, not real prices. Three jars of the same spread: 16 oz for $3.49, 500 g for $3.99, and a twin pack of 2 × 12 oz for $5.00. Convert to one unit (500 g = 17.6 oz; the twin pack is 24 oz), then divide price by size.
| Package | Price | Total | Per oz | vs best |
|---|---|---|---|---|
| 1. Twin pack, 2 × 12 oz | $5.00 | 24.0 oz (680 g) | $0.208 | ✓ Best deal |
| 2. 16 oz jar | $3.49 | 16.0 oz (454 g) | $0.218 | +4.7% |
| 3. 500 g jar | $3.99 | 17.6 oz (500 g) | $0.226 | +8.6% |
The twin pack wins at $0.208 per ounce even though it has the highest shelf price. The 500 g jar costs 8.6% more per ounce: buying 24 oz at its rate would cost $5.43 instead of $5.00, $0.43 more. Open this example in the calculator.
FAQ
How do you calculate unit price?
Divide the price by the size, in one unit: price ÷ ounces, or price ÷ grams × 100 for the price per 100 g. For a multipack, divide by the total: packs × size each. A 16 oz jar at $3.49 is $3.49 ÷ 16 = $0.218 per ounce. The package with the lowest unit price is the better deal, as long as you will use it all.
Should I compare price per ounce or per 100 grams?
Either, as long as every package uses the same one. 1 ounce is 28.35 grams, so a price per ounce × 3.527 is the price per 100 g. US shelf tags usually show per ounce, per pound or per count; UK and EU tags show per 100 g or per kg. This calculator converts ounces, pounds, grams and kilograms for you and shows both.
Is the bigger package always cheaper per unit?
No. Larger, “family size” and “value” packs are often cheaper per unit, but not always: promotions on the regular size, multipacks priced above singles, and a shrunken big pack can all flip it. Compare the unit price every time instead of assuming.
How do I compare multipacks?
Enter the price of the whole multipack, the size of one item, and the number of items in Packs. A 6-pack of 12 fl oz cans is 6 × 12 = 72 fl oz. For toilet paper and paper towels, compare sheets rather than rolls, because “mega” and “double” rolls hold different numbers of sheets: enter the roll count as Packs and the sheets per roll as the size.
Why do shelf-tag unit prices differ between stores and states?
Stores do not all use the same unit. In the US there is no federal unit-pricing rule; some states and cities require shelf unit prices and others leave it to the store, so one tag may say per ounce, another per pound and a third per count, sometimes for two brands on the same shelf. Tags can also show the regular price rather than the sale price, round differently, or be out of date after a pack shrinks. In the UK and EU unit prices are required for most groceries, usually per kg, litre, 100 g or 100 ml. When in doubt, work it out from the net quantity on the pack.
Can I compare ounces with fluid ounces?
No. An ounce (oz) is a weight and a fluid ounce (fl oz) is a volume. They only match for water-like liquids, so converting between them would need the product’s density. The calculator refuses to mix weight and volume rather than give a wrong answer. Many labels print both a weight and a metric volume or weight, so pick one kind for every package.
How does shrinkflation show up in the unit price?
As a higher unit price at an unchanged shelf price. Cutting a pack by a fraction x at the same price raises the unit price by x ÷ (1 − x): 10% smaller is 11.1% more per unit. Put the old and new pack in two rows here, or use the shrinkflation calculator for a single before-and-after change.
More tools: shrinkflation calculator (one pack, before and after) · barcode lookup (current size and recent prices) · how to spot shrinkflation.