Quick answer
A 30g scoop of whey protein has 108 to 114 calories: Myprotein Impact Whey lists 114 kcal with 22g of protein and Myprotein Impact Whey Isolate 108 kcal with 25g, on labels WheyWise checked on 3 October 2026. If you're counting calories, buy the isolate, because almost all of its calories come from the protein itself. Mass gainers are the exception, at 378 kcal in one 100g serving of Myprotein Impact Whey Gainer.
We read the nutrition panel of one widely sold UK product of each protein type on the brand's own website on 3 October 2026, so every figure below is per serving exactly as the label states it.
How many calories are in a scoop of protein powder?
A standard scoop of protein powder has 105 to 123 kcal: Myprotein Impact Whey lists 114 kcal per 30g scoop and Myprotein Impact Whey Isolate 108 kcal, while Myprotein Impact Whey Gainer lists 378 kcal in a 100g serving, checked 3 October 2026. Scoop sizes differ, so compare the serving size as well as the calories.
| Type | Product (flavour) | Serving | Calories | Protein |
|---|---|---|---|---|
| Whey concentrate | Myprotein Impact Whey (Vanilla) | 30g | 114 kcal | 22g |
| Whey isolate | Myprotein Impact Whey Isolate (Vanilla) | 30g | 108 kcal | 25g |
| Vegan | Myprotein Impact Plant Protein (Vanilla) | 30g | 115 kcal | 22g |
| Casein | Bulk Micellar Casein | 30g | 105 kcal | 24g |
| Diet whey | PhD Diet Whey (Belgian Chocolate) | 32g | 123 kcal | 20g |
| Mass gainer | Myprotein Impact Whey Gainer (Brown Sugar Milk Tea) | 100g | 378 kcal | 29g |
Read from each nutrition panel on myprotein.com, bulk.com and phd.com on 3 October 2026. Myprotein says the 100g gainer serving is approximately 3 1/3 scoops. Calories vary a little between flavours.
Why do some protein powders have more calories per scoop?
Protein carries 4 kcal per gram, according to the British Nutrition Foundation, so a scoop with 25g of protein starts at 100 kcal and everything above that comes from fat and carbohydrate. Myprotein Impact Whey Isolate is the closest to pure protein: its 25g of protein account for 100 of its 108 kcal. Myprotein Impact Whey, a concentrate, keeps more of the milk's fat and sugar, with 1.8g of fat and 2.7g of carbohydrate per scoop.
Diet whey is not the leanest option per gram of protein. PhD Diet Whey has 123 kcal for 20g of protein, 6.2 kcal per gram of protein against 4.3 for the isolate, because its ingredient list on phd.com adds waxy barley flour, flaxseed powder and stabilisers to the protein blend. Mass gainers add calories on purpose: Myprotein Impact Whey Gainer gets most of its 378 kcal from 51g of carbohydrate, with oat flour as its first ingredient.
Which protein powder has the fewest calories?
Whey isolate has the fewest calories per gram of protein of the six types we checked: Myprotein Impact Whey Isolate gives 4.3 kcal per gram of protein, against 4.4 for Bulk Micellar Casein, 5.2 for Myprotein Impact Whey and 6.2 for PhD Diet Whey, checked 3 October 2026. You pay for it: Myprotein Impact Whey Isolate costs £1.53 per 25g of protein in the 2.7kg bag at £135.49 on myprotein.com, against £1.16 for Myprotein Impact Whey in the 3.6kg bag at £119.99, so the isolate costs 37p more per 25g of protein and saves 22 kcal.
Fewest calories per gram of protein
MyProtein Impact Whey Isolate Powder
900g bag
The lean choice if you count calories: almost every calorie in the scoop comes from its protein.
or compare all UK prices →Fewest calories per gram of protein
Pros
- + 25g of protein for 108 kcal per 30g scoop (Vanilla)
- + Only 0.9g of fat and 6.1g of carbohydrate per 100g
- + £1.53 per 25g of protein in the 2.7kg bag, checked 3 October 2026
Cons
- – 37p more per 25g of protein than Myprotein Impact Whey in the largest bags
- – The flavoured versions are sweetened with sucralose
●Nutrition per scoop · 24.6g protein in 30g▼
Protein makes up 82%
of this 30g scoop · 108 kcal total
Cheaper per gram of protein
MyProtein Impact Whey Protein Powder
960g bag
Better value per gram of protein if 22 extra kcal per 25g of protein doesn't matter to you.
or compare all UK prices →Cheaper per gram of protein
Pros
- + 114 kcal and 22g of protein per 30g scoop (Vanilla)
- + £1.16 per 25g of protein in the 3.6kg bag, checked 3 October 2026
- + Informed Choice and Informed Protein certified, according to myprotein.com
Cons
- – 1.8g of fat and 2.7g of carbohydrate per scoop, more than the isolate
- – 72g of protein per 100g, against 82g for Myprotein Impact Whey Isolate
●Nutrition per scoop · 21.6g protein in 30g▼
Protein makes up 72%
of this 30g scoop · 113 kcal total
To see every isolate ranked by cost per 25g of protein, use the whey isolate comparison, and if you're choosing a powder for a calorie deficit, read the best protein powder for weight loss.
Frequently asked questions
How many calories are in a protein shake made with water?
The same as the powder, because water adds none. A 30g scoop of Myprotein Impact Whey makes a 114 kcal shake with water and a 30g scoop of Myprotein Impact Whey Isolate a 108 kcal shake, according to myprotein.com on 3 October 2026. Mixing with milk adds the milk's calories on top.
Does diet whey have fewer calories than normal whey?
Not per gram of protein. PhD Diet Whey lists 123 kcal and 20g of protein per 32g scoop, which is 6.2 kcal per gram of protein, against 4.3 for Myprotein Impact Whey Isolate, both checked 3 October 2026. Diet whey adds ingredients such as barley flour and flaxseed, so a plain isolate is leaner.
How many calories are in a mass gainer shake?
Several times a protein scoop. Myprotein Impact Whey Gainer lists 378 kcal, 51g of carbohydrate and 29g of protein in a 100g serving, which Myprotein says is approximately 3 1/3 scoops, checked 3 October 2026.