Most people compare protein powder prices by looking at the total cost of the bag. That's the wrong metric. A £30 bag can be better or worse value than a £50 bag depending on how much protein is actually in it and how heavy the bag is.
The number that matters is: how much does it cost per 100g of powder? Here's how the major UK brands stack up.
The methodology
All prices below are based on the current cheapest available price across tracked UK retailers (including active discount codes where applicable). I'm using the price per 100g of powder — not per 100g of protein, which introduces another variable (protein content per serving varies between products).
For a live view of the cheapest current prices, use the cheap protein powder comparison.
Whey concentrate (budget tier)
This is where the best value lives. Whey concentrate typically sits at 70–82g protein per 100g of powder and costs £1.40–1.80/100g at the best UK prices. MyProtein Impact Whey and Bulk Pure Whey consistently compete at the bottom of this range. See the whey concentrate comparison for today's prices.
The cheapest I've seen for a reputable brand is around £1.35/100g during a major MyProtein sale with a stacked discount code. That's hard to beat.
MyProtein Impact Whey Protein Powder
810g bag
UK's bestselling whey concentrate with 82g protein per 100g. Regularly discounted 40-60% — never pay full price.
See cheapest price →Buy direct from MyProtein →MyProtein Impact Whey Protein Powder
810g bag
UK's bestselling whey concentrate with 82g protein per 100g. Regularly discounted 40-60% — never pay full price.
See cheapest price →Buy direct from MyProtein →Quick verdict
Pros
- + 82g protein per 100g high purity
- + Cheapest per serving during sales
- + Huge 60+ flavour range
- + 5kg bags for long-term savings
Cons
- – Full price is poor value
- – Needs discount code to compete
- – Reformulations change taste occasionally
Quick verdict
Pros
- + 82g protein per 100g high purity
- + Cheapest per serving during sales
- + Huge 60+ flavour range
- + 5kg bags for long-term savings
Cons
- – Full price is poor value
- – Needs discount code to compete
- – Reformulations change taste occasionally
Bulk Pure Whey Protein
2.5kg bag
Budget-friendly Informed Sport tested whey from Bulk with 50+ flavours. Consistently among the cheapest per serving in the UK.
See cheapest price →Buy direct from Bulk →Bulk Pure Whey Protein
2.5kg bag
Budget-friendly Informed Sport tested whey from Bulk with 50+ flavours. Consistently among the cheapest per serving in the UK.
See cheapest price →Buy direct from Bulk →Quick verdict
Pros
- + Among cheapest UK whey options
- + Huge 50+ flavour range
- + 22g protein per 30g scoop
- + Informed Sport batch tested
Cons
- – 70-75% protein purity only
- – Some flavours overly artificial
- – Can cause bloating if lactose-sensitive
Quick verdict
Pros
- + Among cheapest UK whey options
- + Huge 50+ flavour range
- + 22g protein per 30g scoop
- + Informed Sport batch tested
Cons
- – 70-75% protein purity only
- – Some flavours overly artificial
- – Can cause bloating if lactose-sensitive
Whey isolate (mid tier)
Isolate is more processed — lower fat, lower lactose, higher protein per 100g (typically 85–92g). It costs roughly double the concentrate: expect £2.50–3.50/100g for a decent isolate. Browse current whey isolate prices to find the cheapest.
Whether the premium is worth it depends on your situation. If you're lactose sensitive or tracking macros very tightly, yes. If you're just trying to hit a daily protein target cheaply, concentrate is fine.
Bulk Pure Whey Isolate
1kg bag
High-purity whey isolate from Bulk with 27g protein per 30g scoop. Very low fat and lactose, ideal for calorie-conscious or lactose-sensitive buyers.
See cheapest price →Buy direct from Bulk →Bulk Pure Whey Isolate
1kg bag
High-purity whey isolate from Bulk with 27g protein per 30g scoop. Very low fat and lactose, ideal for calorie-conscious or lactose-sensitive buyers.
See cheapest price →Buy direct from Bulk →Quick verdict
Pros
- + 27g protein per 30g serving
- + Very low fat and carbs
- + Suitable for lactose-intolerant
- + Mixes thin and smooth easily
Cons
- – Pricier than concentrate version
- – Thinner mouthfeel less satisfying
- – Fewer flavour options
Quick verdict
Pros
- + 27g protein per 30g serving
- + Very low fat and carbs
- + Suitable for lactose-intolerant
- + Mixes thin and smooth easily
Cons
- – Pricier than concentrate version
- – Thinner mouthfeel less satisfying
- – Fewer flavour options
Casein (slow-release)
Casein digests slowly, which is why it's popular as a before-bed protein. It's typically more expensive than whey concentrate — around £2.00–2.80/100g. Optimum Nutrition Gold Standard Casein is the market leader and can be good value via Amazon when on promotion. Compare casein protein prices across UK retailers.
Vegan protein
Plant-based protein is almost always more expensive per 100g than whey, partly due to processing cost and partly because the market is smaller. Expect £2.00–3.50/100g for a decent pea/rice blend. MyProtein's vegan blend is among the cheaper options. See the vegan protein comparison for the full list.
The honest conclusion
If price per gram is the only thing you care about: buy the biggest bag of MyProtein Impact Whey or Bulk Pure Whey you can find during a sale, with a discount code. That's the cheapest high-quality protein available in the UK, and it's not particularly close.
Check the live comparison table for today's prices — I update it weekly so the numbers above may have changed. For today's discounted products, see the latest protein powder offers. For a broader value guide, read best protein powder UK 2026.
