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How to compare price per unit and spot the better deal

Two products, two different pack sizes, two different prices — which is actually cheaper? The shelf price can't tell you. The only fair measure is the price per unit, and this guide shows how to work it out in seconds.

The fastest way

Enter the price and quantity of each product into the Unit Price Calculator and it shows the per-unit cost of both and tells you which one is the better deal — no mental arithmetic in the aisle.

Why the bigger pack isn't always cheaper

Buying in bulk usually lowers the per-unit price, but not always. A multi-buy promotion on the small pack, an awkward "family size" premium, or rounded pricing can flip the result. Calculating the real number is the only way to be sure rather than trusting the "bigger = cheaper" instinct.

Make sure you compare like with like

Turn the gap into a percentage

Once you know both unit prices, you might want to know how much cheaper one is — "15% less per litre" is more useful than a raw figure. The Percentage Calculator turns the two numbers into a percentage difference, and the Discount Calculator helps when one product is on a sale price.

A note on privacy

The Unit Price Calculator runs entirely in your browser — nothing you type is uploaded — so it works instantly on your phone while you shop.

Open the Unit Price Calculator →

Common questions

What is price per unit?

Price per unit is the cost of a single comparable measure — per litre, per 100 g, per item — rather than the price on the shelf. Dividing the pack price by the quantity turns two differently-sized products into one number you can compare directly, which is the only fair way to tell which is cheaper.

Is the bigger pack always cheaper per unit?

No. Larger packs usually win, but not always — promotions, odd pack sizes, and premium large formats can make a smaller pack cheaper per unit. That is exactly why you calculate it instead of assuming, and the calculator flags which of the two is the better deal.

What if the two products use different units?

Convert both to the same unit first (for example grams to kilograms, or millilitres to litres) so the per-unit prices are comparable. Enter the quantity in matching units for each product and the comparison is apples-to-apples.

Is anything uploaded?

No. The calculation runs entirely in your browser — the prices and quantities you type are never sent anywhere, so you can compare on your phone in a shop aisle with no signup.