If you are trying to hit a protein target without overshooting calories, the most useful number is not protein per 100 grams — it is protein per 100 calories. This single metric, also called protein density, controls for energy and instantly separates lean protein sources from calorie-dense ones.
The answer first
Measured per 100 calories, the leanest everyday protein sources are white fish and shellfish, skinless poultry, canned tuna in water and nonfat Greek yogurt. Whole eggs, lean beef and tofu are solid mid-table options. Nuts, nut butters and hard cheese are genuinely high in protein by weight, but because they are so calorie-dense, their protein per calorie is low.
How to calculate protein density
The formula is simple:
protein per 100 kcal = (protein grams ÷ calories) × 100For example, skinless chicken breast has 31 g of protein and 165 kcal per 100 g. That is (31 ÷ 165) × 100 = 18.8 g of protein per 100 calories. Compare that to almonds: 21.2 g of protein but 579 kcal per 100 g, giving just (21.2 ÷ 579) × 100 = 3.7 g per 100 calories. Both are “high protein” foods by weight, but for the same calories chicken delivers five times the protein.
Best protein sources by protein per 100 calories
The table below ranks common high-protein foods using USDA FoodData Central values, per 100 g of edible portion.
| Food | Protein (g/100 g) | Calories (per 100 g) | Protein per 100 kcal |
|---|---|---|---|
| Shrimp (cooked) | 24.0 | 99 | 24.2 g |
| Canned tuna (in water) | 25.5 | 116 | 22.0 g |
| Skinless chicken breast (roasted) | 31.0 | 165 | 18.8 g |
| Nonfat Greek yogurt | 10.2 | 59 | 17.3 g |
| Beef, 90% lean (cooked) | 26.1 | 176 | 14.8 g |
| Cottage cheese | 11.1 | 98 | 11.3 g |
| Tofu (firm) | 17.3 | 144 | 12.0 g |
| Lentils (cooked) | 9.0 | 116 | 7.8 g |
| Whole egg | 12.6 | 143 | 8.8 g |
| Cheddar cheese | 22.9 | 403 | 5.7 g |
| Almonds | 21.2 | 579 | 3.7 g |
| Peanut butter | 22.5 | 588 | 3.8 g |
The pattern is clear: lean animal proteins and nonfat dairy dominate the top of the list, because they are mostly protein and water with little fat. As soon as a food carries a lot of fat (cheese, nuts, nut butter) or is mostly carbohydrate (most plants), its protein-per-calorie drops.
Why fat and water matter so much
Protein and carbohydrate both supply about 4 kcal per gram, but fat supplies 9 kcal per gram. So a food’s protein density falls sharply as its fat content rises. Cheddar cheese is 22.9 g protein per 100 g — almost identical to canned tuna — but its 33 g of fat pushes calories to 403, dropping protein density to 5.7 g per 100 kcal.
Water content works in the opposite direction. Shrimp, chicken breast and Greek yogurt are high in water, which adds weight and volume without calories, so the calories that remain are mostly protein. That is also why they are filling for relatively few calories.
Plant proteins in context
Legumes such as lentils, black beans and chickpeas are excellent protein sources for a plant-based diet, but they come packaged with carbohydrate, so their protein density is moderate (around 7–8 g per 100 kcal). Tofu does better (about 12 g per 100 kcal) because soybeans are unusually protein-rich. For a fuller side-by-side, see our comparison of tofu vs chicken breast and lentils vs black beans.
How to use this
- For weight management, prioritise the top of the table: lean seafood, poultry and nonfat dairy give the most protein for the fewest calories, which supports satiety.
- For muscle gain on a higher calorie budget, calorie density is less of a concern, so eggs, beef, cheese and nuts all earn their place.
- For a plant-based diet, combine tofu and legumes, and remember that total daily protein matters more than any single food’s density.
You can check the protein density of any individual food on its page — see chicken breast, Greek yogurt or tofu — or scale a serving with our calorie and macro tool.
A note on accuracy
All figures here are USDA FoodData Central reference values per 100 g of edible portion, rounded to one decimal place. Cooking method, cut, brand and trimming change real numbers — drained canned tuna, skin-on chicken or full-fat yogurt will differ. This article is general information, not medical or dietary advice; for personalised protein targets, consult a registered dietitian. Learn more about interpreting these numbers in how to read nutrition data and our methodology.