How WheyWise Tracks UK Protein Prices

A fair question to ask any price comparison site is: where does the data actually come from? Here's an honest answer for WheyWise, written against the code that runs it.

For how WheyWise turns those prices into a score, see how WheyWise scores protein powder.

Where do WheyWise's prices come from?

Every WheyWise price comes from one of three partner sources: Awin product feeds, Partnerize product feeds, or Amazon's product API. None of them involves visiting a retailer's website and reading the page. Each fetch stores the price, the stock status and the time it was fetched, and that database is what powers the comparison tables on this site.

Why no scraping? WheyWise used to read prices from some retailers' own websites. The last of those scrapers were switched off on 16 September 2026, for two reasons. A scraped price from a shop WheyWise could not link to could win the “cheapest” slot while the buy button sent you somewhere else: when we measured it that day, 64% of products with stock showed a cheapest price from a site the button did not lead to. And retailers had started blocking the scrapers, so those prices were going stale. A price from a partner feed or Amazon's API is the price at the place the button actually takes you.

Matching products to Amazon. Amazon listings are matched to products by barcode (GTIN) first. Where there is no barcode match, a stricter name match is used, and uncertain matches go to a review queue rather than straight onto the site.

How is cost per 25g of protein worked out?

WheyWise compares every protein powder on cost per 25g of protein: the price, divided by the grams of protein in the whole pack, multiplied by 25. Raw prices are almost useless for comparison, and even price per 100g of powder misleads, because one powder can carry 59g of protein per 100g and another 90g.

The formula is price ÷ (pack size in grams × protein per 100g ÷ 100) × 25. Here it is with two real products:

The protein figure matters as much as the price, so it gets checked. Where a protein per 100g figure has been checked against the product's label, it is locked so a feed cannot overwrite it. And if a stored figure looks implausible, for example a per-serving number saved as per 100g, the cost per 25g is simply not shown rather than shown wrong. For more on the maths, see how to calculate protein cost per serving.

Which retailers are tracked?

WheyWise tracks the retailers it has a partnership with, plus Amazon UK. Through Awin that means Myprotein, Bulk and Warrior among others; through Partnerize it means Protein Works, and Holland & Barrett for its own Precision Engineered protein range only. Everything else comes through Amazon UK, which is why brands such as Optimum Nutrition, Applied Nutrition and PhD are priced there.

When the same pack is on sale in more than one place, a price fetched in the last seven days takes priority over an older one, even if the older one was lower. If a retailer you use is missing, it usually means there is no partner feed for it yet. The contact page is the place to ask.

How are discount codes added?

Discount codes for partner retailers come in through Awin's promotions feed, and each one is held for approval before it appears on the deals page. WheyWise also has its own code, WW12, which takes 12% off most one-off orders at Protein Works.

Codes from other sources are added by hand when I spot them or when someone sends them in. If you know of a code that's not showing, let me know.

Why might a price differ at checkout?

A price can differ at checkout because it changed after it was last fetched, a sale or code ended, or the retailer prices differently by account, basket or delivery choice. Always check the final price at checkout before buying.

Every price WheyWise holds carries the time it was fetched. A price with no fetch time is never shown, and a price older than 24 hours is never presented as today's best price. One known gap: on subscription-eligible Protein Works products, the feed carries the OnTap subscription price, which is about 15% below a one-off order, so blog posts quote the one-off price instead.

If a price is consistently wrong, that's likely a tracking issue. Report it via the contact page and I'll fix it.

What isn't tracked?

Retailers with no partner feed, and products Amazon does not stock, are not priced on WheyWise. Protein powder is the core of the site, with creatine and pre-workout on the supplements comparison and vitamins on the vitamins section. Protein bars from the Myprotein and Protein Works feeds appear in blog posts only. Within each product, not every flavour and size a retailer sells is in its feed, so the range you see can be narrower than the shop's.

To see what is tracked and compare live prices, head to the price comparison table. To see how prices have moved, use the protein powder price trends tool, and for the cheapest options right now, see cheapest protein per gram in the UK.

Frequently asked questions