Use the price per 100g, kilogram or litre—larger packs are not automatically better value.
The useful answer
When comparing similar products, find the unit price on the shelf label or product page, such as “per 100g” or “per litre”. Compare only matching units, including promotions and family packs.
The quick method
Compare the own-brand unit price with your usual brand, then ask whether you will finish it in time. A lower price is not a saving if food is wasted.
Common catches
One shelf may mix prices per 100g and per item, while online and in-store prices can differ. Treat a loyalty price in the context of whether you will genuinely use that scheme again.