Best Vegan Mass Gainer UK: 5 Powders Compared by Calories and Cost

Written by James, founder of Flaming Phoenix and the maker of Phoenix Bars. Updated October 2026.

The best vegan mass gainer in the UK is the one you will actually use every day, and the easiest to keep using is one you eat rather than drink: Phoenix Bars, our high calorie bars for weight gain, carry up to 557 calories and up to 19g of protein in a compact, 120g bar, with no shaker and no 500ml shake to finish. If you prefer a powder, the label data I checked on 12 October 2026 splits the five like this. Protein Works Vegan Mass Matrix 360 Gold has the most calories per serving at 762 kcal. Bulk Vegan Mass Gainer is the cheapest of the powders per calorie, at about £3.25 per 1,000 kcal on its sale price. USN Wholefood Gainer suits anyone who wants oats and rice instead of maltodextrin, with no soy. Raw Sport Mass Gainer Professional is the only one of the five that is Informed Sport batch tested.

How I compared them

I make a competing product, so here is how this comparison was done. I have not taste-tested these powders. Every figure comes from each brand’s own UK product page on 12 October 2026: serving size, calories, protein, ingredients and price. From those I worked out two numbers the labels do not print. The first is cost per 1,000 kcal, which is the pack price divided by the calories in the pack. The second is calories per gram of what you actually swallow, powder plus the liquid the brand tells you to mix it with. Prices and stock change often, so check the brand page before you buy.

The five powders

Protein Works Vegan Mass Matrix 360 Gold

This has the highest calorie serving here. The nutrition table shows 762 kcal, 51g protein and 117g carbohydrate per 200g serving (the page headline rounds this to 740 kcal). The carbohydrate comes mainly from maltodextrin and oats, the protein from soy, pea and brown rice, and it is sweetened with sucralose. A 1kg bag is £19.99 and holds five servings, which works out at about £5.25 per 1,000 kcal. The 8kg size brings that down to about £3.53.

Bulk Vegan Mass Gainer

This is the lightest serving and the lowest cost. Each 100g serving gives 369 kcal and 31g protein from ultra-fine oats with pea, brown rice, pumpkin seed, flaxseed and quinoa proteins. There is no maltodextrin and it is sweetened with stevia. The 2.5kg pack was £29.99 on sale (£44.99 list), which is about £3.25 per 1,000 kcal on sale and £4.88 at list price. You would need two servings to match one Protein Works shake.

USN Wholefood Gainer

A 125g serving gives 483 kcal and 30g protein. The carbohydrate comes from oat flour, rice flour, sweet potato and tapioca, and the protein from rice and pea. The page states zero soy. It contains gluten from oats and uses sucralose and stevia. At £32 for 2kg it costs about £4.14 per 1,000 kcal.

Raw Sport Mass Gainer

A 100g serving gives 406 kcal and 32g protein from fermented pea protein, with maltodextrin and gluten-free oats. The brand states it is free from gluten, dairy and soya and is lab tested for heavy metals and pesticides. The 2kg pack was £39.99 on sale (£49.99 regular), so about £4.92 per 1,000 kcal on sale and £6.16 at regular price.

Raw Sport Mass Gainer Professional

This is the one for tested athletes. It is Informed Sport batch tested, gluten-free, oat-based with no maltodextrin, and includes creatine. A 125g serving gives 480 kcal and 46g protein. It was £49.99 on sale (£59.99 regular) for the 2.5kg pack the page lists, about £5.21 per 1,000 kcal on sale.

Two others are worth a line. Huel Black Edition is sold as a meal powder, with 400 kcal and about 40g protein per 90g serving, gluten-free, at roughly £4.98 per 1,000 kcal. Naked Nutrition’s Vegan Naked Mass lists 1,230 kcal per serving on its US page, but I could not confirm it ships to the UK, so I have left it out of the ranking.

Cost per 1,000 calories, ranked

From cheapest to dearest on the prices I found: Bulk at about £3.25 on sale, Protein Works 8kg at about £3.53, USN at about £4.14, Raw Sport at about £4.92 on sale, Huel Black Edition at about £4.98, Raw Sport Professional at about £5.21 on sale and Protein Works 1kg at about £5.25.

The number no label shows: how much you have to swallow

A mass gainer serving is not just the powder. Protein Works asks for 200g of powder in 500 to 600ml of liquid, so 762 kcal arrives as 700 to 800g of shake. That is about 1.0 kcal per gram swallowed. The other four land between 0.6 and 0.9 kcal per gram once mixed with water. Mixing with soya milk instead adds roughly 200 kcal per 500ml.

Drinks suit a lot of people, and the NHS suggests high-calorie drinks between meals for anyone trying to gain weight. But if volume is what stops you, it matters. A Phoenix Bar carries up to 557 kcal in only 120g, which is 4.4 to 4.6 kcal per gram, with nothing to mix.

When a powder is the wrong tool

Phoenix Bars are a source of protein, with 18 to 19g per bar, and protein contributes to a growth in muscle mass.

A bar makes more sense when the barrier is effort or volume: no shaker, no blender, no half-litre to finish. Our high calorie bars are vegan, made with gluten-free oats, and can be mixed with water or plant milk to make porridge. They also come first in our best vegan energy bars comparison.

Here is what customers say. Phoenix Bars are rated 4.9 out of 5 from 391 reviews.

“Phoenix Bars are helping me to weight gain prior to Everest next year, which is a big problem for me.” Tim A., November 2025

“Being vegan it’s difficult to find good products.” Oliver H., November 2024

“For its small size, this bar packs a powerful punch in calories.” Lily K., performance nutritionist, September 2025

More than 50 reviewers also mention making the bar into porridge. If you want the full comparison of the best energy bars for weight gain, or the highest calorie bars in the UK ranked per gram, those guides cover the bar options.

Or make your own

A homemade weight gainer shake costs less than any tub. Blend 300ml of fortified soya milk, a banana, two tablespoons of peanut butter and 30g of oats for about 520 kcal. Add a tablespoon of rapeseed oil for another 120.

How to choose

• No shaker, nothing to mix and the least to swallow: Phoenix Bars, our high calorie protein bars.
• Most calories in one shake: Protein Works Vegan Mass Matrix 360 Gold.
• Lowest cost per calorie of the powders: Bulk Vegan Mass Gainer.
• No maltodextrin and no soy: USN Wholefood Gainer.
• Batch tested for drug-tested sport: Raw Sport Mass Gainer Professional.
• Gluten-free claim on the label: either Raw Sport powder.

Whichever you pick, it only works on top of what you already eat. Use the weight gain calculator to find your daily target, then fit it into a weight gain meal plan. If you are plant-based, the high calorie vegan foods ranking shows where the easy calories are.

Common questions

Is there dairy in mass gainer? Most standard mass gainers are built on whey and milk powder. The five here are plant-based, although several are made in factories that also handle milk, so check the allergen line if that matters to you.

Is a mass gainer the same as protein powder? No. Protein powder is mostly protein, at around 100 to 120 kcal a scoop. A mass gainer adds a large amount of carbohydrate to reach 370 to 760 kcal a serving.

Do you need a mass gainer to gain weight? No. Gaining weight comes from eating more calories than you use over time. A gainer is a convenient way to add them, and a Phoenix Bar does the same job with nothing to mix: up to 557 calories in a compact, 120g bar. Food and a homemade shake work too, as the guide on how to gain weight explains.

Which vegan mass gainers are gluten-free? Phoenix Bars are vegan and gluten-free in every flavour, if you would rather eat your calories. Of the five powders, only the two Raw Sport powders carry a gluten-free claim. Bulk, USN and Protein Works contain oats and make no gluten-free claim.

Sources: each brand’s UK product page, checked 12 October 2026. NHS, healthy ways to gain weight. Great Britain nutrition and health claims register. Flaming Phoenix is not affiliated with Protein Works, Bulk, USN, Raw Sport, Huel or Naked Nutrition. All trademarks belong to their owners.