Mass gainers are designed for people who struggle to eat enough calories to support muscle growth. A single serving can pack 300 to 1,200 calories alongside 20-50g of protein — convenient, but not cheap. Per serving, mass gainers are some of the most expensive supplements you can buy.
The good news is that the price spread between brands is enormous. The cheapest mass gainer per 100g can cost half as much as the most expensive. We track mass gainer prices across 85+ UK retailers and update them weekly — this guide shows you the best deals available right now.
Best affordable mass gainers in the UK (2026)
If you just want a quick answer, here are our top picks based on price, protein content, and overall value:
Best overall value
Warrior Mass Gainer delivers 5kg of product at one of the lowest per-100g costs on the market. Solid protein content, simple ingredient list, and consistently in stock.
Best Value
Warrior Mass Gainer Protein Powder - 5kg
5kg bag
One of the most affordable protein powder options in the UK. Strong cost efficiency.
See cheapest price →Buy direct from Warrior →Best Value
Warrior Mass Gainer Protein Powder - 5kg
5kg bag
One of the most affordable protein powder options in the UK. Strong cost efficiency.
See cheapest price →Buy direct from Warrior →Quick verdict
Pros
- + Extremely cheap per serving
- + Decent 30g protein per serving
- + Wide flavour range available
- + Mixes well with a shaker
Cons
- – Very high sugar content
- – Maltodextrin-heavy carb source
- – Overly sweet artificial taste
Quick verdict
Pros
- + Extremely cheap per serving
- + Decent 30g protein per serving
- + Wide flavour range available
- + Mixes well with a shaker
Cons
- – Very high sugar content
- – Maltodextrin-heavy carb source
- – Overly sweet artificial taste
Best from a major brand
Optimum Nutrition Serious Mass is one of the most popular mass gainers in the UK. At 5.4kg it offers good value per 100g from a brand with a strong reputation for quality.
Most Popular
Optimum Nutrition Serious Mass 5.4kg
5.4kg bag
One of the most affordable protein powder options in the UK. Strong cost efficiency.
See cheapest price →Most Popular
Optimum Nutrition Serious Mass 5.4kg
5.4kg bag
One of the most affordable protein powder options in the UK. Strong cost efficiency.
See cheapest price →Quick verdict
Pros
- + 50g protein per serving
- + Added vitamins and minerals blend
- + Trusted established brand
- + Creatine included in formula
Cons
- – Enormous 334g serving size
- – High sugar and maltodextrin
- – Pricier than budget gainers
Quick verdict
Pros
- + 50g protein per serving
- + Added vitamins and minerals blend
- + Trusted established brand
- + Creatine included in formula
Cons
- – Enormous 334g serving size
- – High sugar and maltodextrin
- – Pricier than budget gainers
Best for high protein
Applied Nutrition Critical Mass delivers 42g of protein per 100g — one of the highest protein ratios in the mass gainer category. Good choice if you want calories without sacrificing protein content.
Highest Protein
Applied Nutrition Critical Mass
6kg bag
One of the most affordable protein powder options in the UK. Strong cost efficiency.
See cheapest price →Highest Protein
Applied Nutrition Critical Mass
6kg bag
One of the most affordable protein powder options in the UK. Strong cost efficiency.
See cheapest price →Quick verdict
Pros
- + Industry-leading 42g protein/100g
- + Contains creatine and glutamine
- + Oat flour over pure maltodextrin
- + Lower sugar than most gainers
Cons
- – Premium price for a gainer
- – Thick consistency hard to drink
- – Limited flavour selection
Quick verdict
Pros
- + Industry-leading 42g protein/100g
- + Contains creatine and glutamine
- + Oat flour over pure maltodextrin
- + Lower sugar than most gainers
Cons
- – Premium price for a gainer
- – Thick consistency hard to drink
- – Limited flavour selection
Why mass gainers are expensive
Mass gainers use large serving sizes — typically 100-300g per shake. That means a 2.5kg bag only lasts 8-25 servings. Compare that to whey protein, where a 2.5kg bag gives you 80+ servings. You get through mass gainer much faster, which makes the monthly cost significantly higher.
The main ingredients in most mass gainers are whey protein and maltodextrin (a cheap carbohydrate). Some premium products add oats, MCT oil, creatine, or other extras that push the price up without necessarily improving results.
Cheapest mass gainers in the UK right now
We track mass gainer prices across 85+ UK retailers. The cheapest options right now are Warrior Mass Gainer (around £0.52/100g), Optimum Nutrition Serious Mass (around £0.65/100g), and PSN Hard Gainer (around £0.66/100g).
Prices rotate depending on sales and stock levels. The mass gainer price comparison shows every product we track ranked by cost per 100g with live prices updated weekly.
Pure Source Nutrition PSN Hard Gainer Powder
3kg bag
One of the most affordable protein powder options in the UK. Strong cost efficiency.
See cheapest price →Pure Source Nutrition PSN Hard Gainer Powder
3kg bag
One of the most affordable protein powder options in the UK. Strong cost efficiency.
See cheapest price →Quick verdict
Pros
- + Solid 5kg bag great value
- + Simple transparent ingredients
- + Reasonable protein-to-calorie ratio
- + Good for hardgainer bulking
Cons
- – Lesser-known brand fewer reviews
- – Bland taste reported by users
- – Grainy texture when mixed
Quick verdict
Pros
- + Solid 5kg bag great value
- + Simple transparent ingredients
- + Reasonable protein-to-calorie ratio
- + Good for hardgainer bulking
Cons
- – Lesser-known brand fewer reviews
- – Bland taste reported by users
- – Grainy texture when mixed
Best mass gainer for beginners
If this is your first mass gainer, you do not need the most calorie-dense product on the market. Start with something that has a reasonable protein-to-calorie ratio and is easy on the stomach. Look for:
- At least 20g protein per 100g
- 300-500 calories per serving (not 1,000+)
- Oat-based rather than pure maltodextrin
- A brand you can buy in smaller sizes to test first
Optimum Nutrition Serious Mass ticks most of these boxes and is widely available. Applied Nutrition Critical Mass is another strong option with higher protein content.
DIY mass gainer — is it cheaper?
A popular alternative to buying a mass gainer is making your own from whey protein, oats, and peanut butter. Here is a rough cost comparison:
- Commercial mass gainer — typically £2-4 per serving (300-500 kcal per serving)
- DIY: whey + oats + peanut butter — roughly £1-1.50 per serving for a comparable calorie and protein content
The DIY approach is almost always cheaper because you are buying each ingredient at its lowest cost per gram rather than paying for a pre-mixed product. The trade-off is convenience — a ready-made mass gainer just needs water, while DIY requires a blender and more prep time.
If you go the DIY route, start with cheap whey concentrate. The cheapest whey concentrate in the UK is your base — add 80-100g of instant oats and a tablespoon of peanut butter for a 500+ calorie shake at a fraction of the mass gainer price.
What to look for in a mass gainer
Not all mass gainers are created equal. Here is what actually matters:
- Protein per serving — Aim for at least 30g per serving. Some cheap mass gainers are mostly maltodextrin with very little protein.
- Calorie source — Oat-based mass gainers tend to be better quality than pure maltodextrin ones. Check the ingredient list.
- Price per 100g — This is the fairest comparison metric because serving sizes vary enormously between brands. Our comparison table normalises everything to per-100g cost.
- Added extras — Creatine, vitamins, and digestive enzymes are nice-to-haves but are usually cheaper bought separately. Do not pay a premium for a mass gainer just because it includes creatine.
The options that score best on protein content while staying affordable are Applied Nutrition Critical Mass (42g protein/100g) and Warrior Mass Gainer (around £0.52/100g). Both are featured in our top picks above.
When to use a mass gainer vs extra food
Mass gainers make sense in a few specific situations:
- You genuinely cannot eat enough whole food to gain weight (fast metabolism, small appetite)
- You need a portable, quick calorie source between meals
- You are in a dedicated bulking phase and need 3,500+ calories daily
If you can eat enough through regular meals, whole food is almost always cheaper and more nutritious than a mass gainer. The supplement is a convenience tool, not a requirement.
Best mass gainer under £30
On a tight budget? Several mass gainers come in under £30 for a full-size bag. Warrior Mass Gainer regularly comes in around £26, and Pro-Elite XForce sits around £24 for a 4kg bag.
Pro-Elite XForce Mass Gainer 4Kg Bag
4kg bag
One of the most affordable protein powder options in the UK. Strong cost efficiency.
See cheapest price →Pro-Elite XForce Mass Gainer 4Kg Bag
4kg bag
One of the most affordable protein powder options in the UK. Strong cost efficiency.
See cheapest price →Quick verdict
Pros
- + Budget-friendly entry-level gainer
- + Added BCAAs in formula
- + Smooth mixability for a gainer
- + Decent chocolate flavour options
Cons
- – Lower protein ratio than rivals
- – Only 4kg bag less value
- – Maltodextrin dominant carbs
Quick verdict
Pros
- + Budget-friendly entry-level gainer
- + Added BCAAs in formula
- + Smooth mixability for a gainer
- + Decent chocolate flavour options
Cons
- – Lower protein ratio than rivals
- – Only 4kg bag less value
- – Maltodextrin dominant carbs
Stock and prices change weekly. For the full list sorted by price, check the live mass gainer comparison table.
Find the cheapest mass gainer for you
Mass gainer prices fluctuate a lot between retailers and across sales events. The mass gainer price comparison shows every product we track ranked by cost per 100g. For active discount codes that might bring the price down further, check the protein powder deals and discount codes.
If budget is your biggest constraint, seriously consider the DIY route. A bag of cheap whey protein plus supermarket oats will give you more servings for less money than any commercial mass gainer on the market.
