UK Supermarket Price Comparison: How Tracking Works in 2026

Introduction

Which UK supermarket is cheapest? It's one of the most-searched retail questions in Britain — and the honest answer is "it depends on the basket, and it changes weekly." Tesco, Sainsbury's, ASDA, Morrisons, and Aldi all move prices constantly, run different promotions, and win on different categories. This post explains how supermarket price comparison actually works with data, and what it reveals.

Why "cheapest supermarket" isn't a fixed answer

No single grocer is cheapest on everything. One wins on staples, another on branded goods, another on fresh. And they all reprice and promote weekly. So a credible comparison isn't a one-off snapshot of a few items — it's a consistent basket, tracked over time, across all the major grocers.

The basket approach

The standard method mirrors how the UK's own inflation measures work: define a representative basket of products, then price that exact basket at each supermarket, repeatedly.

A worked example

Illustrative sample data — not real prices.

Same basket, five grocers

Category winners

The headline "Aldi cheapest" is true for this basket — but the category view shows Tesco wins household with promotions, which a total-only comparison hides.

What the data reveals

• Promotion strategy. Who discounts what, how deeply, and how often.
• Category positioning. Where each grocer chooses to be cheapest to build price perception.
• Price movement. How the "cheapest" shifts week to week — nobody holds the crown permanently.
• Own-label vs branded. Where the real value gaps sit.

How to put it to work

• Define a representative, matched basket.
• Track effective prices (after offers) at each grocer.
• Repeat weekly to capture movement.
• Break down by category to see who wins where.
• Watch promotions, not just shelf prices.

The takeaway

UK supermarket price comparison is a basket-and-time exercise, not a snapshot. Track a consistent basket across Tesco, Sainsbury's, ASDA, Morrisons, and Aldi over time, adjust for promotions, and break it down by category — and "who's cheapest" becomes a clear, defensible, continuously updated answer instead of a guess.

FAQ

Which UK supermarket is cheapest?

It depends on the basket and the week — discounters often lead on staples, but category winners vary and prices move constantly, so only ongoing basket tracking gives a reliable answer.

What is the basket method?

Pricing a fixed, representative set of matched products at each supermarket repeatedly, so comparisons are fair and track change over time.

Why adjust for promotions?

Because shelf price isn't what shoppers pay; effective price after offers reflects true cost.

Conclusion

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