Unit Price Comparator
Compare two products by price per gram, ml or item. Enter both packs and this unit price comparator shows the price per 100 g, per 100 ml or per item for each one, and which one is really cheaper.
Item A
Item B
How to use this unit price comparator
This unit price comparator takes two products and works out which one is really cheaper. The shelf price alone cannot tell you that, because two packs hold different amounts. You only need three numbers for each item, and the result updates as you type.
Step 1: Enter the first item: its price, how much is in the pack, and the unit — grams, kilograms, millilitres, litres or pieces.
Step 2: Enter the second item the same way. The tool converts kilograms to grams and litres to millilitres for you, so you can compare packs written in different units.
Step 3: Read the result: the price per 100 g, per 100 ml or per item for each product, which one is cheaper, and how much cheaper it is in percent.
Worked example
A bag of rice costs $5 for 500 g. Another bag costs $8 for 1 kg. The second bag looks more expensive on the shelf — $8 against $5 — but which one is really cheaper?
Divide each price by its weight. The $5 bag is $5 divided by 500 g, which is $1.00 per 100 g. The $8 bag is 1 kg, and 1 kg is 1,000 g, so it is $8 divided by 1,000 g — $0.80 per 100 g.
The second bag is cheaper by 20%: the difference of $0.20 divided by the higher price of $1.00 is 0.20, or 20%. You pay less per gram and you get twice as much rice. That is the whole point of a unit price comparator.
Why the bigger pack is not always cheaper
Shops put a big number on the shelf ticket: the price of the whole pack. That number hides the amount inside. A giant pack can look like a bargain and still cost more per gram than a small one, because the price does not rise in step with the weight.
Pack sizes are chosen to sell, not to make maths easy. One brand sells 400 g, another sells 500 g, a third sells 750 g. The prices look close, but the price per 100 g can be very different. Only the unit price tells the truth, because it puts every pack on the same footing.
Special offers make it worse. A buy one get one free deal, a smaller pack at a lower price, a big pack with a loud discount sticker — each one needs the same check. Work out the unit price and the winner is usually clear.
Which unit to compare
Use grams for food that is weighed: rice, flour, coffee, cheese, washing powder. The tool shows the price per 100 g, which is the number most shelf labels use, so you can check your answer against the shop’s own label.
Use millilitres for liquids: milk, juice, shampoo, cooking oil. Pick millilitres or litres — the tool converts litres to millilitres for you — and compare the price per 100 ml.
Use pieces for things sold one by one: batteries, eggs, nappies, bin bags. The tool shows the price per item, which is the only fair way to compare a pack of 8 with a pack of 12.
One rule matters above the rest: always compare the same base unit. Price per 100 g against price per 100 ml is meaningless, because grams and millilitres measure different things. This unit price comparator will ask you to pick the same kind of unit for both items if the two do not match.
Frequently asked questions
What is unit price?
Unit price is what one gram, millilitre or item costs. It is the shelf price divided by the amount you get, so two different packs can be compared fairly.
Why compare per 100 g instead of the pack price?
The pack price hides the amount inside. A bigger pack can cost more overall while costing less per gram, or the other way round. Only the price per 100 g (or per 100 ml, or per item) shows which one is really cheaper.
How do I handle kg and litres?
The tool converts them for you — 1 kg is 1,000 g and 1 litre is 1,000 ml. Just pick kg or litres in the unit box and enter the amount as shown on the pack.
What if both cost the same per unit?
Then neither one is cheaper, and you can pick either one. The tool will tell you that both cost the same per unit, so the choice comes down to size, brand or expiry date.
Does the cheaper unit price always win?
Not always — check the expiry date and whether you will use it all before it goes bad. The cheapest price per gram is no bargain if half of it ends up in the bin.