Price per kilo

What it's for

Two packs of the same product, one of 380 grams at 2.49 and one of 500 at 3.09: which is better? By eye you can't tell, and using a calculator in front of the shelf wastes time. Here you put in price and weight and out comes the price per kilo and the price per hundred grams, the two measures products are really compared with.

The unit price is already on the label, but small

In European shops the shelf label has to show, besides the price, the price per unit of measure: it's a rule made precisely to allow comparison. It's printed small, often in a corner, and nearly always goes unnoticed. It's worth looking for: where it exists, this page is only needed for the cases where it's missing, for online shopping (where it often is) or to compare two different shops.

The «family pack» isn't always cheaper

It's the commonest and most mistaken idea in the supermarket. It often happens that the big pack costs more per kilo than the medium one, because the big price is read as «a stock-up» and not as «a price per kilo». It happens above all on promoted lines: three small packs on offer nearly always beat the big format at full price.

Watch out too for two legitimate but tricky things: the drained weight (in a tin of pulses or tuna the real product is less than the gross weight, and that's the number to use) and the quiet shrink in contents, the pack that goes from 500 to 460 grams at the same price. Price per kilo shows it immediately, the price on the label doesn't.

Nearby tools

For a liquid product the right comparison is per litre: the conversion is done by Volume converter, and for weights Weight converter. If you're comparing two discounts, the real percentage is given by Discount percentage, and to see what a recurring cost really adds up to there is Annual subscription cost.