Affordable Mass Gainer UK: A Smarter Buyer's Guide for 2026

For readers who want the short version, here are the top picks based on price, protein content, and overall value.

Rank	Product	Best for	ProteinDeals verdict
1	Warrior Mass GainerFrom £9.99 Pros +59.7% below the £1.24/100g average across 18 comparable /compare listings +24g protein per 100g	Best overall	ships 5kg of product at one of the lowest per-100g costs on the market, with solid protein content, a simple ingredient list, and reliable stock levels.
2	Optimum Nutrition Serious MassFrom £82.00 Pros +15g protein per 100g +Available from the named UK retailer Cons −21.5% above the £1.24/100g average across 18 comparable /compare listings	Best-value alternative	is one of the most widely bought mass gainers in the UK. At 5.4kg it delivers good value per 100g from a brand with a long track record on quality.
3	Applied Nutrition Critical MassFrom £27.99 Pros +54.8% below the £1.24/100g average across 18 comparable /compare listings +24g protein per 100g	Specialist option	packs 42g of protein per 100g, one of the highest protein ratios in the category. It suits anyone who wants extra calories without giving up protein density.

Mass gainers use large serving sizes, typically 100 to 300g per shake. A 2.5kg bag only stretches to 8 to 25 servings, compared with 80+ servings from the same size bag of whey protein. You get through the tub far faster, which pushes the monthly cost noticeably higher than a standard protein powder.

Most mass gainers are built from whey protein and maltodextrin, a cheap carbohydrate source. Premium versions add oats, MCT oil, creatine, or other extras that raise the price without necessarily improving results, so it pays to check whether those additions are worth paying for.

Tracking prices across 85+ UK retailers currently puts Warrior Mass Gainer (around £0.52/100g), Optimum Nutrition Serious Mass (around £0.65/100g), and PSN Hard Gainer (around £0.66/100g) at the front of the pack.

Prices shift with sales and stock levels, so today's cheapest pick is not guaranteed to hold. The mass gainer price comparison ranks every product we track by cost per 100g, updated weekly.

A first mass gainer does not need to be the most calorie-dense product available. Look for something with a sensible protein-to-calorie ratio that sits well on the stomach.

1. 1

   At least 20g protein per 100g, so calories are not coming from carbs alone.

2. 2

   300 to 500 calories per serving, rather than 1,000 or more.

3. 3

   Oat-based rather than pure maltodextrin, for a steadier calorie source.

4. 4

   A brand available in smaller sizes, so you can test the taste before committing to a bigger bag.

A common alternative to a commercial mass gainer is blending your own from whey protein, oats, and peanut butter. Here is a rough cost comparison for a similar calorie and protein profile.

Building your own shake is almost always cheaper because each ingredient is bought at its own lowest cost per gram, rather than paying a markup for a pre-mixed product. The trade-off is convenience: a commercial mass gainer needs only water, while DIY needs a blender and a few extra minutes of prep.

If you take the DIY route, start with cheap whey concentrate as the base. The cheapest whey concentrate in the UK works well here. Add 80 to 100g of instant oats and a tablespoon of peanut butter for a 500+ calorie shake at a fraction of the commercial price.

1. 1

   Commercial mass gainer: typically £2 to £4 per 300 to 500 kcal serving.

2. 2

   DIY blend (whey, oats, peanut butter): roughly £1 to £1.50 per serving for a comparable result.

Mass gainers vary a lot in quality. These are the factors that actually affect value and results.

1. 1

   Protein per serving. Aim for at least 30g. Some budget mass gainers are mostly maltodextrin with very little protein, so check the label rather than trusting the marketing.

2. 2

   Calorie source. Oat-based formulas tend to outperform pure maltodextrin blends for sustained energy, so read the ingredient list before buying.

3. 3

   Price per 100g. This is the fairest comparison metric because serving sizes vary enormously between brands. Our comparison table normalises everything to cost per 100g.

4. 4

   Added extras. Creatine, vitamins, and digestive enzymes are nice to have but usually cheaper bought separately, so there is little reason to pay a premium for a mass gainer just because it includes them.

A mass gainer earns its place in a few specific situations.

Outside of those situations, whole food is almost always cheaper and more nutritious than a mass gainer. Treat the supplement as a convenience tool rather than a requirement for building muscle.

1. 1

   You genuinely cannot eat enough whole food to gain weight, whether from a fast metabolism or a small appetite.

2. 2

   You need a portable, quick calorie source between meals.

3. 3

   You are in a dedicated bulking phase and need 3,500+ calories daily.

On a tighter budget, several mass gainers come in under £30 for a full-size bag. Warrior Mass Gainer regularly sits around £26, and Pro-Elite XForce comes in around £24 for a 4kg bag.

Stock and pricing shift weekly, so check the live mass gainer comparison table for the current full list sorted by price.

Mass gainer prices move a lot between retailers and across sales periods. The mass gainer price comparison lists every product we track ranked by cost per 100g. For active discount codes that could push the price down further, check the protein powder deals and discount codes.

If budget is the main constraint, the DIY route is worth serious consideration. A bag of cheap whey protein plus supermarket oats delivers more servings for less money than any commercial mass gainer on the market.