Supermarket Price Comparison Calculator
Compare two supermarket offers by unit price, even when the packs are different sizes. Enter the total price paid, the packs included and the amount in each pack to see the fairer comparison.
How to use Supermarket Price Comparison Calculator
1. Choose the currency used for results. 2. Enter the total price for each offer, the number of packs it buys and the amount in each pack. Choose compatible units, such as g and kg. 3. Change a value to update the results, or select Calculate. Review the chart and notes with the total. 4. Use Copy results, Share results or Download result graphic to keep the answer. Shared links include your figures. 5. Reset restores the editable example inputs.
Why use this tool?
The cheapest pack on the shelf can have a higher unit price. Different pack sizes and multibuy offers make the mental arithmetic harder, especially when one label uses grams and another kilograms. This comparison converts matching units before dividing the price by the total quantity. It is a useful starting point for similar products. A lower unit price is less useful if you do not want the product, cannot store it or are likely to waste the extra amount.
How the calculation works
Total quantity = packs × quantity per pack × unit conversion. Kilograms are converted to grams and litres to millilitres. Unit price = total price paid ÷ total quantity × 100 for weight or volume, or × 1 for items. The two results are compared before display rounding. Mass can be compared with mass, volume with volume and item counts with item counts. The calculator rejects a mass-versus-volume comparison because converting between them would require a product-specific density. Enter the price after a promotion or discount, not the original price as well.
Example
Offer A costs £3.60 for 750 g, so it is £0.48 per 100 g. Offer B costs £4.50 for 1 kg, so it is £0.45 per 100 g. B has the higher pack price but is cheaper per 100 g by £0.03.
Practical tip
For a two-pack offer, set packs to two and enter the total offer price. Keep the quantity field as the amount in one pack.
Frequently asked questions
Can I compare grams with kilograms or millilitres with litres?
Yes. The tool converts those units within the same type of quantity. It will not automatically compare grams with millilitres.
How do I enter a buy-one-get-one-free offer?
Enter the total amount you pay, set packs to two and enter the size of one pack. The free pack contributes to total quantity without adding another price.
Does the cheaper unit price mean I should buy it?
The result only compares price per quantity. Quality, ingredients, convenience, storage and how much you will use can still matter.