Quick answer: 500 g for 12.50 is 12.50 ÷ 0.5 = 25.00 per kg, and 1 kg for 22.00 is 22.00 per kg, so the larger pack is 12% cheaper per kilogram.
How it's calculated
Unit price = price ÷ quantity in a common unit. Grams are turned into kilograms (500 g = 0.5 kg), millilitres into litres, ounces and pounds into kilograms (1 oz = 28.35 g, 1 lb = 453.59 g), so both products are compared on the same basis.
The saving is the difference in unit price divided by the higher unit price. The calculator also shows the difference per 100 g or 100 ml, the way many shelf labels state it.
A lower unit price is only a saving if you will use it all: a large pack that goes off before you finish it can cost more in the end.
Worked examples
- 500 g for 12.50 vs 1 kg for 22.00: 25.00 vs 22.00 per kg → B is 12% cheaper
- 1.5 L for 4.50 vs 6 × 330 ml for 7.20: 3.00 vs 3.64 per litre → A is 17.5% cheaper
- Pack of 30 for 27 vs pack of 12 for 12: 0.90 vs 1.00 per item → A is 10% cheaper
Frequently asked questions
How do I compare a multipack?
Multiply the size of one item by the number in the pack: 6 cans of 330 ml are 1,980 ml.
Can I compare grams with millilitres?
No. Weight and volume are different measures; compare products that are labelled the same way.
Is the shelf unit price always right?
It is usually reliable, but labels can use different bases (per 100 g, per kg), so working it out yourself makes the comparison fair.
Is the bigger pack always cheaper?
Not always. Shops sometimes charge more per kilo for the big pack, or put the small one on offer, which is exactly why it's worth checking.
How do I count an offer like buy 2, get 1 free?
Enter what you actually pay and what you actually get: the price of two, and the size of three.
Does VAT change the comparison?
Not if both prices are on the same basis. Shelf prices in Saudi Arabia and the UAE already include VAT, so compare them as they are.