Aldi crowned the cheapest supermarket in May

Aldi has been crowned the cheapest supermarket for the fifth month running, according to our latest analysis. 

The supermarket has kept the momentum from its 2025 overall win, having taken the title across 10 months of the 12. It was only beaten by Lidl in July and October last year. 

Read on to find out how other supermarkets, including Lidl and Sainsbury's, compare – and how much you could save by switching supermarkets.

Cheapest supermarket in May

We checked the prices of 95 popular branded and own-brand groceries, including milk, cheese and Hovis sliced bread, at eight of the UK's biggest supermarkets throughout May to see how they compared.

The table shows how much our shopping cost on average:

Aldi secured the cheapest supermarket title in May, with an average price of £168.30 for our list.

Lidl, with Lidl Plus discounts, came second with an average price of £170.58. Without Lidl Plus discounts, our shop came to £170.66 – a difference of only 8p. 

Asda came in fourth, with our list of items costing £192.58.

Tesco with a Clubcard was next, at £196.88, followed by Morrisons (£197.50) and then Sainsbury’s with Nectar (£198.79).

Waitrose was again the most expensive supermarket in our monthly analysis, with the items on our list costing £235.49 on average throughout May. This is a difference of £67.19 or nearly 40% compared with Aldi.

There were 41 loyalty discounts overall in May for our smaller list: 22 at Sainsbury's, 18 at Tesco, and one at Lidl.

• Find out more: Cheapest supermarkets of 2026

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How much of a discount do loyalty cards give?

Having a loyalty card would save an average of 2.67% at Tesco and 3.58% at Sainsbury's over the month, while at Lidl you would only save a tiny 0.05%. 

Last month, Lidl announced a big change to its loyalty card scheme. Now customers collect points rather than reward coupons, with £1 spent equalling one point. This brings the scheme into line with both Nectar and Clubcard.

The discounts offered by loyalty cards may sound good, but that's only if you can access them. Our research has found that millions of people can't access loyalty promotions because they're not eligible to join the supermarket schemes due to their age, lack of address or difficulties with digital access. 

In February, Tesco announced that it planned to make its Clubcard available to under-18s this year. The move comes after a major campaign launched by Which? urging supermarkets to lift their unfair restrictions on their loyalty schemes. 

Although this is a win for consumers, more work is needed as certain restrictions continue to lock people out of valuable savings. Groups often affected include those without smartphones and under-18s, who may struggle to access – or simply not know how to access – loyalty prices.

• Find out more: Loyalty schemes compared

What has happened to the longer list?

We will no longer publish research on the longer list of groceries as part of our monthly cheapest supermarket analysis, which included more branded items as well as own-brand items.

Instead, each month we will publish our research on the cheapest supermarket for branded groceries separately, which we think will be of more use to shoppers as it will allow us to make more granular price comparisons. 

This new monthly tracker won't include Aldi and Lidl, as they don’t stock the same range of branded goods as the non-discounter supermarkets.

• Interested in more than just price? Shoppers have rated product quality, customer service, online deliveries and more to reveal the best and worst supermarkets.

What's happening to grocery prices?

 The UK inflation rate slowed to 2.8% in the year to April, according to the Office for National Statistics (ONS). The fall was larger than expected thanks to the reduction in the government's energy price cap.

Grocery inflation fell to 3.1% in the four weeks to 17 May, according to Worldpanel by Numerator. This is the slowest rate of increase since December 2024.

The easing of inflation is welcome news for shoppers who have been grappling with warnings of a rise in food prices due to the impact of the war in the Middle East.

Shoppers leant on promotions to keep costs down, with 30.3% of sales including a deal last month – up from 28.4% a year ago. Spending on promoted items rose 9.5% year on year, while full price spending was virtually flat, growing by only 0.1%.

• Find out more: Check what's happening to prices by supermarket, category of food and ranges using the Which? food and drink inflation tracker

How Which? finds the cheapest supermarket

We check the prices of hundreds of grocery items at eight major supermarkets, using an independent price comparison website. 

For each supermarket, we calculate the average price of each item across the month, then add those up to get each supermarket's average total price. 

What items are on the list?

Our shopping list comprises the country’s most popular and widely available groceries, based on extensive market analysis. 

It includes branded items such as Cathedral City cheddar and Hellmann's mayonnaise, as well as own-brand products such as potatoes and baked beans. 

Own-brand items won’t be identical across supermarkets, but we’ve ensured everything we’ve compared is as similar as possible, based on several factors, including quality and weight.

Which? never shares the full list of products used in its analysis, to avoid supermarkets attempting to skew the results. 

We don't want supermarkets to compete with one another to lower prices only on the items they know they'll be judged on. Instead, we want retailers to work to make groceries affordable across the depth and breadth of their available lines.

What about special offers and loyalty prices?

We include special offers but not multibuy discounts. 

We can only include loyalty prices that apply to all members of a scheme (where there's one price on the shelf for shoppers with a loyalty card and another for those without). Currently, this type of two-tier pricing is used at Lidl, Morrisons, Sainsbury's, Tesco and Waitrose. 

We're unable to include discounts that are personalised to selected members, and we can’t factor in points or other rewards, as these vary between customers and don't always have a quantifiable monetary value.

• Find out more: how to spend less at the supermarket