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How to compare unit prices at the supermarket

By Robin Lange · · updated

The unit price is the price per kilo, litre, 100 grams or item, printed in small type on the shelf ticket next to the shelf price. To find the better value between two packs, compare the unit price, not the shelf price, and make sure both tickets use the same unit. New Zealand and Australia require larger grocery retailers to show unit prices, Great Britain requires every trader to (small shops are exempt for pre-packed goods), and the US has no federal rule, though some states set their own. Correct as of October 2026.

What a unit price is, and where to find it

A shelf ticket usually shows two prices. The big one is what you pay for the pack. The small one, often in a corner or along the bottom edge, is the same price worked out per standard amount: “$3.20 per kg”, “£1.50 per litre”, “45c per 100 g” or “$0.75 each”.

How to compare two packs

  1. Find the unit price on each ticket. It’s the small price per kilo, litre, 100 g or item, or in the US per ounce, pound or fluid ounce.
  2. Check both tickets use the same unit. If one says per 100 g and the other per kg, multiply the first by 10. If one says per ounce and the other per pound, multiply the first by 16.
  3. If a ticket has no unit price, work it out. Divide the pack’s price by its weight or volume, and measure both packs in the same unit.
  4. Pick the lower unit price, as long as you’ll use the whole pack before it goes off.

Or put both packs in here. As you type, it shows each pack’s unit price (per kg, litre or item, or per lb or fl oz for US units) and which is cheaper. Packs sold by weight, by volume and by count can’t be compared with each other.

Pack A
Pack B

Three worked examples:

Rice: 1 kg for $3.50, or 5 kg for $16.00.

The big bag is 30 cents a kilo cheaper. Check: 5 × $3.20 = $16.00.

Cheese: a 500 g block for $8.50, or a 1 kg block for $18.00.

Here the smaller block is cheaper. Check: 0.5 × $17.00 = $8.50.

Cereal (US): a 12 oz box for $4.29, or an 18 oz box for $5.99.

The bigger box is about 2.5 cents an ounce cheaper. Check: 18 × 33.3¢ = about $5.99.

Common traps

Different units on neighbouring tickets. One ticket might say “$1.70 per 100 g” and the one beside it “$18.00 per kg”. Multiply the first by 10 and it’s $17.00 per kg, so it’s the cheaper one. Convert before you compare. The same goes for “per 100 mL” against “per litre”.

Per item against per amount. Twelve rolls of 180 sheets for $9.00 is 75c a roll; nine rolls of 300 sheets for $10.80 is $1.20 a roll. Per roll the first pack wins. Per sheet it doesn’t:

Specials and multi-buys. A 1 kg tub of yoghurt at $6.00, or 2 for $10.00, is $6.00 per kg for one and $5.00 per kg on the deal. That’s only good value if you’ll eat 2 kg before it goes off. Check whether the ticket shows the unit price for the single price, the deal price, or both.

Club and member prices. Many tickets now show two prices, each with its own unit price. A 750 g pack at $4.50, or $3.80 for members, works out to $6.00 per kg ($4.50 ÷ 0.75) and about $5.07 per kg ($3.80 ÷ 0.75). Compare the prices you’ll actually pay: if you’re a member, use the member unit price wherever a pack has one; if you’re not, ignore member prices.

Drained weight. Canned tuna, beans and fruit are packed in liquid. A 185 g can of tuna might hold only 130 g of fish. At $2.60, that’s about $1.41 per 100 g by net weight but $2.00 per 100 g of actual tuna. A 425 g can (290 g drained) at $5.80 looks cheaper by net weight (about $1.36 per 100 g), but by drained weight it’s the same $2.00 per 100 g. Read the drained weight on the label when it’s there.

What the law requires

Country Rule Who must show unit prices Units Applies from
New Zealand Consumer Information Standards (Unit Pricing for Grocery Products) Regulations 2023 Stores of 1,000 m² or more, and online sellers, that sell all ten listed grocery categories Per 100 g or 100 mL; per kg for meat, seafood, fruit and vegetables; per litre for drinks Stores 31 August 2024; online 31 August 2025
Australia Unit Pricing Code (Competition and Consumer (Industry Codes Unit Pricing) Regulations 2021) Stores with more than 1,000 m² of grocery display space, online grocery retailers, and retailers who opt in Per 100 g or 100 mL; per kg for meat, fruit and vegetables, cheese; per litre for drinks 1 October 2021
Great Britain Price Marking Order 2004, amended in 2024 and 2025 Traders selling goods to consumers; shops of 280 m² or less are exempt for pre-packed goods of fixed size Per kg, per litre or per item 2004; current rules from 6 April 2026
United States No federal law; state rules vary Depends on the state NIST model rule: one consistent unit for all sizes of a product Varies

New Zealand

The regulations cover stores with at least 1,000 square metres of floor space that sell bread, dairy, eggs, fruit, vegetables, meat, fish, rice, sugar and packaged food, and online sellers of the same range. A smaller store that chooses to show unit prices must follow the same rules. The unit price must be at least a quarter of the font size of the shelf price, and if a store shows a cheaper price for club members, it must show a unit price for that price too. Loyalty-points prices are exempt.

Australia

The Unit Pricing Code has applied since 1 October 2021. On 1 September 2025 the Government released a consultation paper on strengthening it: clearer display, more retailers covered, more consistent units and penalties for breaches. In May 2026 it said it was still considering the outcome. As of October 2026 the code has not been amended.

Great Britain

From 6 April 2026, amendments to the Price Marking Order require unit prices per kilogram or litre (or per item), and when a product has a loyalty price, both the normal and loyalty unit prices must be shown. A multi-buy such as “£4 each or 2 for £7” needs both unit prices too, though offers across mixed products (say, any six bottles) are exempt. For canned food in liquid, the unit price must use the drained weight. The Order applies in England, Scotland and Wales.

United States

There is no federal unit pricing law. NIST’s 2025 Unit Pricing Guide lists 16 states, plus the District of Columbia, Puerto Rico and the US Virgin Islands, with unit pricing laws or regulations, including Connecticut, Massachusetts, New Jersey, New York and Oregon. Some of these only set rules for stores that choose to show unit prices. NIST’s model regulation asks that every size of a product use the same unit, so ounces sit beside ounces.

Keeping a running total

The free shopping calculator on this site runs in your phone’s browser: type in each price as it goes in the trolley and it keeps the total.

Sources

All accessed 7 October 2026.