Unit Price Calculator
Find out which product is better value by comparing price per unit. Works with weight, volume, or item count. Mix units freely — e.g. compare grams vs kilograms.
How the Unit Price Calculator works
Enter the price and quantity for two products, select the unit for each, and click Compare. The calculator converts both products to the same base unit — grams for weight, millilitres for volume, or items for counted products — then works out the cost per 100g, per 100ml, or per item and tells you which represents better value.
Unit pricing is one of the most powerful tools for stretching a grocery budget. In UK supermarkets, the shelf label usually includes a unit price, but it can be hard to spot or may use inconsistent units across products. This calculator eliminates the guesswork, especially when comparing a 400g tin against a 500g bag, or a 1 litre bottle against a 330ml can.
You can mix units freely — for instance, compare a product sold in grams with one sold in kilograms and the calculator will normalise them automatically. Note that weight and volume are not directly comparable, so ensure you are comparing like with like: solid foods by weight, liquids by volume.
Frequently asked questions
Why is unit pricing useful when shopping?
Unit pricing lets you compare products on a like-for-like basis regardless of pack size or price. A larger pack often has a lower cost per unit than a smaller one, but not always — retailers sometimes price larger sizes at a premium or offer better deals on smaller packs during promotions. Checking the unit price before buying ensures you get the best value for money rather than assuming bigger is always cheaper.
Are supermarket unit prices always accurate?
UK supermarkets are required to display unit prices on shelf labels, but errors do occur. Prices on shelves can lag behind till prices after a change, and promotional items are not always updated correctly. It is worth double-checking unit prices on the shelf label and using a calculator to verify, particularly for products where the pack size makes mental arithmetic difficult.
How do I compare products with different units?
To compare products with different units — such as grams versus kilograms — convert everything to a common base unit first. For weight, convert to grams; for volume, convert to millilitres. This calculator handles unit conversion automatically, so you can enter 500g for one product and 1kg for another and it will compare them correctly on a per-gram basis.
What is the best unit to use when comparing groceries?
For solid foods, price per 100g is the most widely used comparison unit in UK supermarkets and makes it easy to compare similar products. For liquids, price per 100ml is standard. For items sold by count — such as teabags, eggs, or nappies — price per item is the most intuitive measure. Always compare products using the same base unit to ensure the comparison is meaningful.