Enter the price and quantity for two items. Use the same unit for both items — for example, both in grams, both in litres, or both as number of items.
The shelf price or discounted price for item A.
Use the quantity in the selected unit.
Optional. Use 0 if there is no discount.
The shelf price or discounted price for item B.
Use the same unit as item A.
Optional. Applied before the unit price is calculated.
Result
Item B is cheaper
Item B costs £0.0050 per g compared with £0.0060 per g for item A.
Item A unit price£0.0060/g
Item B unit price£0.0050/g
Saving per unit£0.0010/g
Percentage saving16.67%
Item A: £3.00 ÷ 500g = £0.0060 per g.
Item B: £5.00 ÷ 1,000g = £0.0050 per g.
Important: only compare like with like. If one item is in grams and another is in kilograms, convert them to the same unit before comparing.
How the unit price calculator works
A unit price shows the cost of one unit, such as one gram, one litre, one serving or one item. The lower unit price is usually the better value, as long as the products are genuinely comparable.
Adjusted price = Price × (1 − Discount % ÷ 100)
Unit price = Adjusted price ÷ Quantity
Saving per unit = Higher unit price − Lower unit price
Percentage saving = Saving per unit ÷ Higher unit price × 100
Unit prices only make sense when both items are measured in the same way. Comparing £3 for 500g with £5 for 1kg is fine if you calculate both per gram or both per kilogram.
Per gram£3 ÷ 500g = £0.006 per g.
Per kilogram£3 for 500g is the same as £6 per kg.
Wrong comparisonDo not compare price per gram with price per kilogram directly.
Best-value checkThe cheaper unit price wins only if the product quality and amount you need are similar.
Unit price examples
Item A
Item B
Better value
Why
£3.00 for 500g
£5.00 for 1kg
Item B
£0.005/g vs £0.006/g
£2.50 for 2L
£1.40 for 1L
Item A
£1.25/L vs £1.40/L
£10 for 12 items
£8 for 10 items
Item B
About £0.80/item vs £0.83/item
Common unit price mistakes
Comparing different units: convert grams to grams, litres to litres, or items to items before judging value.
Ignoring discounts: apply the discount first, then calculate the unit price.
Assuming bigger is always cheaper: larger packs are often cheaper per unit, but not always.
Buying more than you need: the cheaper unit price is not always a saving if the extra food, product or material is wasted.
Related everyday maths calculators
Unit price comparisons often connect to discounts, ratios and percentage savings.