Unit Price Comparator

The Unit Price Trick Supermarkets Don't Want You to Use

Retailers price products strategically to obscure true value. A larger package is not always cheaper per unit. This calculator strips away the confusion and illustrates which option gives you more for your money.

The Mistakes Most People Make at the Checkout

Many people find themselves reaching for the bigger package almost automatically, assuming it is always the better deal. It is not always that simple. A promotional sticker or a bold "family size" label can make a product feel like a bargain when the numbers tell a different story. It can help to pause and think in terms of price per gram rather than price per package. One approach is to treat every shopping trip as a small exercise in comparison. The difference in unit price between two products might seem trivial, but across a weekly shop it is worth noting how those small gaps add up over time.

What This Calculator Actually Shows You

This tool works as an illustration of relative value between two products at a given moment. Prices change, promotions come and go, and pack sizes are sometimes quietly adjusted by manufacturers. Many people overlook the fact that a product's weight can shift even when the packaging looks identical. Using a unit price comparison regularly, rather than just occasionally, is one approach that many shoppers find genuinely useful for building better habits around everyday spending.

Run it with sensible defaults

Using product 1 price of 3.99, product 1 size of 400, product 2 price of 6.49, product 2 size of 750, the calculation works out to 0.0087/unit. The defaults are meant as a starting point, not a recommendation.

The levers in this calculation

The inputs — Product 1 Price, Product 1 Size, Product 2 Price, and Product 2 Size — do not pull with equal force.

How the math works

This tool divides each product's price by its size to calculate unit price, then identifies the lower unit price as the better value. The comparison assumes consistent quality and usability across products, with no additional fees or bulk discounts applied beyond the listed price.

Using the result to negotiate

The figure gives you a concrete number to quote when shopping alternatives. "I'm paying £X annually" cuts through marketing in a way "I want a better deal" doesn't. The specificity wins.

What this doesn't capture

Usage varies month-to-month; tariffs change; discounts come and go. The figure here is a clean baseline — your actual annual bill will fluctuate around it. Use the calculation to benchmark providers, not as a prediction of a specific bill.