Unit Price Comparison Calculator
Enter the price, quantity and unit of two products to see the unit price of each, which one is the better buy and the percentage difference.
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Formula
Unit price = price ÷ (quantity × size of the unit in kg, litres or items)Cheaper by % = (higher unit price − lower unit price) ÷ higher unit price × 100Dearer by % = (higher unit price − lower unit price) ÷ lower unit price × 100- Unit sizes: 1 lb = 0.45359237 kg, 1 oz = 1/16 lb, 1 US gal = 3.785411784 L, 1 US fl oz = 1/128 US gal. Mass units compare only with mass, volume with volume, and items with items.
Worked example
Product A: 500 g for 2.50 is 2.50 ÷ 0.5 = 5.00 per kg. Product B: 1.2 kg for 5.40 is 5.40 ÷ 1.2 = 4.50 per kg. B is cheaper: it costs (5.00 − 4.50) ÷ 5.00 = 10% less than A, and A costs (5.00 − 4.50) ÷ 4.50 = 11.11% more than B.
Frequently asked questions
How do I compare prices of different sizes?
Divide each price by its quantity in the same unit. 500 g for 2.50 is 5.00 per kg, and 1.2 kg for 5.40 is 4.50 per kg, so the larger pack is cheaper.
How is the percentage difference worked out?
With unit prices of 5.00 and 4.50, the cheaper one costs (5.00 - 4.50) / 5.00 = 10% less, and the dearer one costs (5.00 - 4.50) / 4.50 = 11.11% more. Both are shown because they differ.
Can I compare grams with ounces or litres with gallons?
Yes, within the same kind of unit. Mass units (g, kg, oz, lb) compare with each other, as do volume units (ml, l, US fl oz, US gal). 16 oz equals 1 lb equals 0.45359237 kg exactly.
Is the bigger pack always cheaper?
No. Bulk packs are often cheaper per unit, but not always. 12 eggs at 3.60 cost 0.30 each and 6 eggs at 2.10 cost 0.35 each, yet a promotion can reverse this, so always check the unit price. Also consider whether you will use it all before it spoils.