Learning how to use unit prices is one of the simplest ways to spend less at the supermarket without changing what you eat. The unit price tells you what one gram, one litre, or one item actually costs, so you can compare two packs fairly instead of guessing which one is the better deal. The bigger pack is not always cheaper, and the smaller pack is not always a rip-off. Once you know where to look and how to read the number, a normal weekly shop can quietly get cheaper.
- The unit price shows the cost per gram, litre, or item, so packs of different sizes can be compared fairly.
- A bigger pack is not always cheaper — always check the shelf-edge unit price before deciding.
- Pair unit-price checks with a shopping list and a quick pantry check to avoid buying duplicates.
What Is a Unit Price and Where to Find It
A unit price is the cost of a standard amount of a product. On most supermarket shelf labels it sits next to the pack price, usually in smaller print, and reads something like “£0.45 per 100g” or “$2.10 per litre”. It exists so shoppers can compare a 400g tin with a 800g tin, or a branded box with a store-brand box, without doing mental maths in the aisle. If your store does not show unit prices, you can work them out yourself by dividing the pack price by the pack size — a phone calculator does this in seconds.
How to Use Unit Prices When You Shop
Start with the items you buy every week, such as rice, pasta, cooking oil, coffee, and washing powder. These are the products where a small per-unit difference adds up over a year. Compare the unit price, not the pack price, and pick the lower one — unless the larger pack will go off before you use it. A cheaper per-unit price is only a saving if you actually use the product. For fresh food, balance the unit price against how much your household will eat before the use-by date.
Watch out for pack sizes that look similar but are not. A box that shrinks from 500g to 450g while keeping the same price has quietly become more expensive per unit, and the unit price is what reveals it. The same trick applies to multipacks: divide by the number of items inside, not by the number of packs, before comparing with a single large pack.
A cheaper per-unit price is only a saving if you actually use the product.
Common Unit Price Mistakes to Avoid
The first mistake is assuming the biggest pack always wins. Bulk packs can carry a higher unit price than a medium pack on promotion, especially when a smaller size is discounted. The second mistake is comparing unlike units — grams against kilograms, or millilitres against litres — which makes the numbers meaningless. Convert both to the same unit before deciding. The third mistake is ignoring quality and taste: if the cheapest per-unit option is a product nobody in the household likes, it will sit in the cupboard, and that is not a saving at all.
- Compare the unit price, not the pack price, when sizes differ.
- Check multipacks per item, not per pack.
- Watch for packs that shrink while the price stays the same.
- Only buy bulk when you will use it before it goes off.
Putting Unit Prices Together With a Shopping List
Unit prices work best alongside the basics of a cheaper shop. A shopping list stops impulse buys, and a quick check of what is already in the cupboard stops duplicates — both habits pair naturally with unit-price comparisons, as our guide to saving money on laundry shows for household costs. The same disciplined approach helps bigger goals too, whether that is saving for your first car or simply keeping the weekly food bill steady. And once the shopping is home, easy weeknight dinners turn those well-chosen ingredients into meals without extra takeaway spending.
Try it on your next shop: pick five regular items, note their unit prices, and choose the lowest per-unit option each time. You will quickly learn which of your usual brands are genuinely good value and which ones only look like it.
What to Watch Next
Unit prices are a small habit with a steady payoff. Keep checking the shelf-edge number on your regular items, stay alert for shrinking pack sizes, and only buy bulk when you know the food will be used in time. Over weeks of shopping, those small per-unit wins add up to a noticeably lower grocery bill without cutting the foods you enjoy.