Supermarket offers change frequently, but the method for judging them does not. This practical guide explains how to compare Tesco Clubcard deals, Sainsbury’s offers, Asda groceries deals, Morrisons promotions, Aldi Specialbuys and Lidl offers UK shoppers may encounter, using unit prices, basket totals and realistic household needs rather than headline discounts alone.
Overview
Finding the cheapest weekly shop is rarely as simple as choosing the supermarket with the most visible promotions. A discount may apply only with a loyalty card, require several items to be purchased, exclude certain sizes, or encourage spending on products you did not plan to buy. The useful question is not “How large is the saving?” but “What will this item cost me, and does it reduce the cost of my actual basket?”
A repeatable comparison can be built around four figures:
- Shelf price: the price before any offer or loyalty reduction.
- Offer price: the price you pay after a valid promotion.
- Unit price: the cost per kilogram, litre, item or another useful measure.
- Basket cost: the total paid for the products you genuinely need.
This approach works across supermarket offers this week in the UK, including loyalty pricing, multi-buys, reduced household products and seasonal promotions. It also helps avoid treating Aldi or Lidl as automatically cheaper, or assuming a large pack represents better value. Prices, pack sizes and local availability can vary, so the calculation should always be based on the products and stores available to you.
How to estimate the real saving
Start with a shopping list divided into three groups: essentials, useful replacements and optional purchases. Compare offers only within the first two groups unless the optional item is already part of your budget. This prevents a promotion from turning a saving into extra spending.
For a single product, use:
Unit price = total price ÷ quantity
For example, if a hypothetical 750g product costs £3.00, its price is £4.00 per kilogram. A different 1kg product priced at £3.60 costs £3.60 per kilogram, even though its shelf price is higher. The larger pack is therefore cheaper by unit, assuming both products meet the same need and quality is acceptable.
For a multi-buy, calculate the effective price per item:
Effective unit price = promotional total ÷ number of items
Using an illustrative offer of three items for £5.00, the effective price is £1.67 per item when all three will be used. If you would normally buy only one, compare the £5.00 outlay with the cost of buying one item at its standard price. The promotion may lower the unit price while increasing this week’s bill and creating waste.
To estimate the value of a loyalty offer, compare the price you would otherwise pay:
Saving = regular price − eligible offer price
Then calculate the basket result:
Basket saving rate = total saving ÷ regular basket cost × 100
Do not include points, vouchers or cashback in the calculation until you know their conditions and practical value. Treat them as a separate benefit rather than an immediate reduction unless they can be used reliably on a future shop.
Inputs and assumptions
A fair supermarket comparison needs consistent inputs. Record the following before deciding where to shop:
- Product specification: brand, size, flavour, dietary requirement or household use. Comparing a premium branded product with a basic alternative may produce a misleading result.
- Quantity needed: the number of units your household will use before the use-by, best-before or quality window becomes a concern.
- Loyalty eligibility: whether the offer requires Tesco Clubcard, a Sainsbury’s Nectar account or another store loyalty scheme, and whether you have access to it at checkout.
- Minimum spend: any threshold needed to activate a voucher, delivery benefit or basket promotion.
- Travel and delivery: include fuel, public transport, parking, delivery charges or the value of your time when comparing separate shops.
- Substitutions and availability: an online price is useful only if the item is available, and a planned in-store deal may not be present at every branch.
Keep the comparison focused. It is usually more useful to compare ten regular products across two or three convenient supermarkets than to price every item across every retailer. A cheaper product that requires an additional journey may not reduce the total cost.
Loyalty schemes can be valuable when they reduce products you already buy. Check the displayed price and any terms before checkout, especially where an offer is limited to selected sizes, flavours, quantities or dates. The same principle applies to cashback offers: compare the final cost after any confirmed reward, but do not spend more simply to reach a reward threshold.
Worked examples
Example 1: comparing pack sizes
Suppose a household is choosing between a 500g pack at £2.20 and a 750g pack at £3.00. The first costs £4.40 per kilogram. The second costs £4.00 per kilogram, so the larger pack is cheaper per kilogram by £0.40. If the household will use the extra quantity, the 750g pack is the stronger value. If some will be wasted, the smaller pack may still be the better purchase overall.
Example 2: testing a multi-buy
Imagine a cleaning product priced at £2.10 individually or offered as three for £5.40. The multi-buy works out at £1.80 each, saving £0.30 per item compared with the individual price. Buying three saves £0.90, but only if all three are needed and stored safely. If the products would otherwise sit unused, the realistic saving is lower than the advertised saving.
Example 3: comparing two weekly baskets
Assume a planned basket contains ten products. Supermarket A offers £6.00 in loyalty reductions, producing a food total of £48.00. Supermarket B has lower shelf prices on some items and produces a total of £46.50, but requires a separate journey costing an estimated £2.00. In this example, Supermarket A costs £48.00 in goods, while Supermarket B costs £48.50 after travel. The cheaper shelf total is not the cheaper complete shop.
These figures are illustrative rather than current supermarket prices. Replace them with the prices shown in your local store or online account, and recalculate when pack sizes or offers change.
When to recalculate
Revisit your comparison whenever pricing inputs change. Useful triggers include the end of a loyalty promotion, a change in pack size, a new multi-buy, a change to your household’s dietary needs, or a switch between delivery and in-store shopping. Recalculate before a larger stock-up, because a promotion can be worthwhile for durable goods but unsuitable for fresh food.
It is also sensible to review your method after several shops. Compare your estimated basket with the receipt total and note why they differ. Common causes include substitutions, forgotten items, impulse purchases, delivery charges, unavailable promotions and offers that required a loyalty scan. This turns a one-off price check into a useful household savings record.
For a practical weekly routine, check the official supermarket offer pages or app, select the products already on your list, record the regular and promotional prices, then calculate unit prices and the final basket total. Check Tesco Clubcard deals, Sainsbury’s offers, Asda groceries deals, Morrisons offers, Aldi Specialbuys and Lidl offers UK shoppers may be considering, but choose the shop that gives the best total value for your needs and journey. If you also use vouchers or cashback, verify their terms before checkout. For related methods, see our supermarket savings guide covering Clubcard, Nectar and cashback offers and our guide to UK supermarket offers and loyalty rewards.
