Quick answer: Start with one real receipt, choose one item you buy regularly, compare equivalent packs by unit price, then ask whether you will use the whole pack before it spoils. Include delivery and membership costs in the total you actually pay. Repeat the comparison after a shop. A loyalty price or a larger pack can be good value, but neither is automatically the cheapest usable food for your household.
Saving money on food is a decision about cash paid and food used, not just the number on a shelf label. You do not need an ideal weekly menu or nine different supermarket accounts to start. This guide gives a small, repeatable method for a UK household. It makes no promise of a fixed weekly saving, a cheapest national chain or a live Smaklig price-comparison service. Examples below are deliberately hypothetical, not current shop prices or tested meal costs.
First, find the number you can change#
Take your most recent grocery receipt or online order confirmation. Include food, delivery, collection and any fee you actually paid for that order. Separate household goods if you want a food-only total; do not compare a food-only shop with a receipt that also contains toiletries. Note the date, shop or delivery channel, and how many people the food was intended to serve. One receipt is a starting point, not proof of a normal week.
Mark just three things: a food bought but not used, a regular item whose brand or pack size could change, and a promotion you would not otherwise have bought. That makes your next shop an experiment with a clear comparison. MoneyHelper's food-budget guidance recommends setting a shopping budget and checking that offers are for things you need; it also suggests considering own-brand ranges. It does not prove that every weekly shop, own brand or offer is cheaper for you.
| Record after the shop | Why it matters |
|---|---|
| Total paid, including applicable charges | This is money that actually left your account. |
| Food purchased and size of each pack | A recipe's used-ingredient allocation is not the checkout bill. |
| Food carried into the next shop | A remainder is still useful only if stored safely and then used. |
| Food discarded | A low unit price may have produced an expensive usable portion. |
You can use paper or a note on your phone. Do not invent a monthly saving by multiplying one unusually good shop by four.
Compare the same thing in the same unit#
The Competition and Markets Authority (CMA) explains that unit pricing expresses a price per standard weight, volume or item. Look for £/kg, £/litre or pence per item beside the selling price. Convert both options to the same unit before comparing. A 100 g figure and a 1 kg figure differ by a factor of ten. Check net and drained weights when the foods are packed in liquid: 400 g on the front of a tin is not automatically 400 g of usable beans.
Here is a made-up arithmetic example, not a price observed at any UK retailer:
| Option | Cash needed today | Shelf unit price | If this household eats only 750 g |
|---|---|---|---|
| 750 g pack | £1.80 | £2.40/kg | £1.80 paid; £2.40 per kg eaten |
| 1 kg pack | £2.10 | £2.10/kg | £2.10 paid; if the other 250 g is discarded, £2.80 per kg eaten |
The 1 kg pack has the lower shelf unit price. If the remaining 250 g is eaten safely later, it may be the better purchase. If the household predictably discards it, the smaller pack has lower cash outlay and lower cost per kilogram actually eaten. The example assumes the food in the pack is otherwise equivalent and ignores any preparation loss; it does not say that all larger packs create waste.
The CMA found that larger packs, promotions, multipacks and prepacked produce are not always the best value per unit. Unit prices can also change by shop and date. Check the actual label or online listing each time rather than relying on a rule such as “bulk is cheaper”.
Give a promotion a four-part test#
For an offer, ask: Would I buy this item without the offer? What is the price per comparable unit? Will I use the extra quantity safely? What is my full checkout total? If any answer is unknown, do not treat the advertised percentage as a household saving.
The CMA's 2024 review of supermarket loyalty pricing found that member offers generally saved against the same product's usual price, but some loyalty-priced items were cheaper elsewhere. That finding is about the promotions the CMA examined at that time, not a guarantee for today's item or for every Tesco, Sainsbury's, Morrisons, Waitrose or Lidl offer. Membership eligibility, the specific product, shop format, postcode, stock and channel need checking at the point of purchase. Compare a relevant alternative you would really buy; a discount on an unnecessary purchase is still spending.
For delivery or collection, compare the complete order: goods at the prices you qualify for, delivery or collection charge, any minimum-basket effect and any membership cost allocated honestly to the period you use it. Keep cash paid at this checkout separate from an allocated cost for a membership you already paid for; adding the whole prepaid fee again to today's cash would double-count it. A lower basket subtotal does not settle the comparison if the second option needs a fee or an extra trip. Do not count petrol as zero if a distant shop requires a drive, but do not assign an invented travel cost either. For a regular shop, your own receipts provide a better decision record than an undated headline claiming one chain is cheapest.
For example, imagine the hypothetical £2.10 pack above is delivered with a £2 charge and you previously paid £12 for a membership you expect to use for 12 shops. Today's new cash outlay for the pack and delivery is £4.10; the comparison cost is £5.10 when you allocate £1 of that earlier membership payment to this shop. The £1 is an accounting share, not another charge today. If you eat 750 g and safely carry the remaining 250 g into the next shop, record 250 g of usable food carried forward, not an instant £0.53 cash refund or a second purchase. On the next shop, record £0 new pack spend for that carried 250 g if you actually use it; keep its original cost allocated to the first pack. If it spoils instead, the pack's cost per kilogram eaten becomes £2.80/kg as calculated above. These invented figures illustrate the ledger method, not a real offer or a measured saving; compare the full basket and actual fees before making a buying decision.
Reduce waste without bending food-safety rules#
Before buying a second fresh pack, check what you already have, its storage instructions and its date. Plan a use for the amount left only if it can be used safely. A freezer or cupboard alternative can help when a fresh item will not be eaten in time; compare the actual packs and labels rather than assuming any format is always cheaper. The NHS confirms that fresh, canned and frozen fruit and vegetables can count towards 5 A Day, with specific advice for canned products. This is a nutrition option, not a price ranking.
Use-by is a safety date; best-before concerns quality. Food Standards Scotland says food past a use-by date must not be eaten even if it looks and smells fine; freezing may be possible up to that date when the pack permits it. Follow the pack's storage instructions. FSA advice for England, Northern Ireland and Wales gives more detail on chilling and freezing. Do not use a budget target as a reason to eat food after its use-by date. If you cook extra portions, use the relevant FSA leftover guidance and any more specific pack directions; this article is not a substitute for them.
Run one honest two-shop experiment#
Choose one change for your next shop: a smaller pack you will finish, an equivalent own-brand item after checking its label and unit price, or declining an offer that was not on your list. Keep the rest of the basket roughly comparable. After the following shop, look at actual receipts and what remains usable. If the first shop included a large pack carried forward, credit the second shop for the food actually used, not for a projected saving on day one.
A useful note is: “I paid £___ for this pack; ___ g was eaten; ___ g remains safely stored; ___ g was discarded.” Fill those blanks from real purchases. The method can reveal a saving, no difference or a trade-off you still prefer for convenience. It does not assume that a family of four, a single shopper and someone with limited freezer space should make the same choice.
For a complete weekly menu, use a meal-planning guide. For a waste-cost audit, record discarded food separately. For a specific chain's offer conditions, use that chain's current terms and a retailer guide once published. This article owns the cross-shop decision method, not cheap dinner recipes, a sub-£3 recipe claim, national waste statistics or live retailer rankings.
Common questions#
Is the biggest pack always cheapest?#
No. The CMA found that bigger packs are not always cheapest per unit. Even when a larger pack has the lowest shelf unit price, compare the cash required today and how much your household will actually use before buying it.
Does a loyalty price mean I should switch shops?#
No automatic conclusion follows. The CMA found many genuine discounts against a product's usual price in its 2024 study, but also examples cheaper elsewhere. Check today's relevant alternatives, access conditions and full trip or delivery cost.
Will switching to frozen vegetables save money?#
It might, depending on current prices, pack sizes and how much you waste. Frozen vegetables can count towards 5 A Day, but that does not make them universally cheaper. Compare equivalent usable quantities and the actual checkout total.
Can I use food after its best-before date?#
Best-before usually marks quality, whereas use-by marks safety. Follow storage instructions and the product's condition; some foods have particular rules. Never extend a use-by date using smell or appearance.
AI-generated content. Always verify ingredients and allergen information yourself. Check the actual product label, storage instructions and any dietary requirements before buying or serving food.
Editorial sources checked 23 September 2026: CMA unit-pricing guide; CMA loyalty-pricing review; MoneyHelper food budgeting; NHS 5 A Day; Food Standards Scotland date labels; FSA chilling/freezing; FSA cooked leftovers. Check current prices, pack details and any changing offer terms before shopping.
Sources and further reading
- A short guide to unit pricing — Competition and Markets Authority
- Loyalty pricing in the groceries sector — Competition and Markets Authority
- Use-by and best-before dates — Food Standards Scotland
- Cooking your food — Food Standards Agency
- How to chill, freeze and defrost food safely — Food Standards Agency
- Paying your own way: food budgeting — MoneyHelper
- What counts towards 5 A Day — NHS