How we measure

What AisleBench Essentials is

Every week we price the same 21 everyday groceries at six UK supermarkets: Aldi, Asda, Lidl, Morrisons, Sainsbury's and Tesco. We add them up and publish two numbers for each supermarket:

• the basket total, in pounds: what those 21 items cost at the prices shown that week;
• the AisleBench Essentials Index: the same total, set to 100 in our first published week, so you can see how each supermarket's prices have moved since.

We publish each total twice: once at the price anyone pays, and once at the price a loyalty card holder pays (Clubcard, Nectar, Lidl Plus and similar).

What it is not

• It is not a measure of inflation or the cost of living. It has no sales figures and no household spending weights. It answers one question: what does this basket cost here, this week? It is not comparable with the Consumer Prices Index, and we never present it that way.
• It is not a stock check. A price on display counts, even if the item is shown out of stock. We say so beside the total when that happens.
• It does not cover a whole supermarket's range. It covers 21 items chosen to be comparable at all six.

The basket (version 1.0)

Version 1.0 applies from the collection of Thursday 22 October 2026. The basket was tested privately for four weeks before that.

Why these items

They are everyday items that all six supermarkets sell in a comparable form. We checked the list against the Office for National Statistics' 2026 consumer price basket: 19 of the 21 items correspond to an item the ONS prices, and the other two (vegetable oil, digestives) to one of its product groups. The basket is our own selection. It is not based on, weighted like or endorsed by the ONS basket.

Two items we wanted are tracked separately, not in the total, because the supermarkets don't sell them in the same size:

• bananas: one supermarket sells only a 6-pack where the others sell 5;
• potatoes: three sell 2kg bags where the others sell 2.5kg.

How we match products

• One fixed product per supermarket for each item. We name it, and we price the same product every week. We don't hunt for the cheapest alternative each week.
• The standard own-label range, not the value range and not the premium range.
• Pack sizes must match within 10%. We never scale a price up or down to a standard size: the total only contains prices a shopper can actually see and pay.
• Where a supermarket can't meet the specification exactly, we say so. In version 1.0:
  • Tea: Aldi and Lidl don't sell an everyday 80-bag pack, so their "Gold" 80-bag tea is used. It is their dearer range, so this works against them, not for them.
  • Beef mince: only Aldi and Lidl sell chilled 10% fat mince. Sainsbury's is 12%; Asda, Morrisons and Tesco are 15% (Tesco's is labelled steak mince). This is the least like-for-like item in the basket.
  • Toilet tissue: Morrisons' and Sainsbury's 4-roll packs have 190 sheets a roll, against 220 elsewhere. We show the price per 100 sheets beside the total, but the total uses the pack price.
  • Washing-up liquid: Morrisons' own-label is 450ml.
  • Sugar: Asda and Morrisons sell no own-label granulated sugar, so a branded 1kg bag is used.

What each release contains

• A short summary:
  • the lowest tracked total;
  • each supermarket's standard and loyalty-card totals;
  • the week's movement;
  • any missing-price or availability warnings;
  • notable offers and price changes.
• The complete weekly snapshot, linked from the summary: all 21 items at all six supermarkets. For each it gives:
  • the exact product and pack size;
  • the standard and loyalty-card price;
  • any offer terms;
  • the availability shown;
  • the source and when it was checked;
  • any accepted departure from the specification.

The complete weekly snapshot is published as a readable table, so anyone can check and challenge the result. A CSV with the headline basket totals and index results is also available to download.

• Changes of product are highlighted in the snapshot. Earlier snapshots stay published, unchanged.

Where the prices come from

So Lidl's prices come from a shelf, and everyone else's from a website. We show the source next to every price and never present one as the other.

Lidl prices are observations from the store where they are read. We don't present them as proof that Lidl charges the same price everywhere.

When

AisleBench records the basket every Thursday, all six supermarkets on the same day, and normally publishes the results on Friday. Each price carries the date it was checked. Exact collection timestamps are kept in AisleBench's internal audit record.

• No fixed hour is promised. Any delay or incomplete collection is stated in the release.
• After a bank holiday or a failed collection, we publish on the next practical working day, showing when the prices were actually read and when they were published.
• Prices read on another day are never passed off as Thursday's.

The two totals: everyone, and loyalty card holders

• Standard: the lowest price anyone can pay without a loyalty card, including a public offer when the basket quantity qualifies for it.
• Member: the lowest advertised loyalty-card price available to any ordinary member, or the standard price where there isn't one.

Some offers don't count:

• Multibuys ("2 for £3") don't change the total, because the basket buys one of each. We still record them.
• Personal coupons and targeted offers are excluded from both totals. Not everyone gets them, and they can't be checked.
• Shelf-tag wording such as "Price Match" or "Low Everyday Price" is not counted as a reduction.

The gap between the two totals shows how much of a supermarket's value depends on having its card.

The index

The index sets each supermarket's basket total to 100 in our first published week. A reading of 103 means that supermarket's basket costs 3% more than it did then. It compares each supermarket with its own starting point, so it shows movement rather than which supermarket is cheapest. The pound totals show that.

When a price is missing

• A price on display counts, even when the item is shown out of stock.
• If no price is shown, there is no price. We never estimate one and never carry last week's forward.
• We only name a cheapest supermarket when all six have a price for every item. If one doesn't, we compare all six on the items they all have, and say how many ("20 of 21 items").
• A supermarket's index line has a visible gap for any week it couldn't be fully priced. When it returns, it carries on from its original starting point; it never restarts at 100.
• An item with no price for three weeks in a row is reviewed, and may be replaced. A replacement is a new basket version (see below).

In the four test weeks, 1 of 504 prices was missing.

Changes and corrections

• The basket is versioned. Any change to an item, a specification or a matched product gets a new version number and the date it applies from. Earlier weeks are never recalculated on the new basket.
• Corrections are shown, not hidden. If we publish a price that turns out to be wrong, we correct it, keep a record of the original, and say what changed and why.

Version history