What macros are
Macronutrients ("macros") are the three nutrients that provide almost all the energy in food: protein, carbohydrate and fat. Alcohol also has calories (7 kcal per gram) but is not a nutrient you need. Each macro gives a fixed amount of energy per gram, which is what lets you turn a calorie target into grams:
| Macro | Energy | Main roles |
|---|---|---|
| Protein | 4 kcal per gram | Building and repairing muscle and other tissue, enzymes, fullness |
| Carbohydrate | 4 kcal per gram | The body's preferred fuel for the brain and hard exercise |
| Fat | 9 kcal per gram | Hormones, cell membranes, absorbing vitamins A, D, E and K |
grams = daily calories × percentage ÷ 100 ÷ kcal per gram
Worked examples
On 2,000 kcal with a high-protein 30 / 40 / 30 split (protein / carbs / fat):
- Protein: 2,000 × 30% = 600 kcal ÷ 4 = 150 g
- Carbohydrate: 2,000 × 40% = 800 kcal ÷ 4 = 200 g
- Fat: 2,000 × 30% = 600 kcal ÷ 9 = 66.7 g
| Calories and split | Protein | Carbs | Fat |
|---|---|---|---|
| 2,000 kcal, balanced 20 / 50 / 30 | 100 g | 250 g | 66.7 g |
| 2,500 kcal, custom 25 / 45 / 30 | 156.3 g | 281.3 g | 83.3 g |
| 1,800 kcal, keto 20 / 5 / 75 | 90 g | 22.5 g | 150 g |
If you enter your weight, the calculator also shows protein per kilogram. For the first example at 70 kg, 150 g of protein is 2.14 g/kg, at the upper end of what is useful for strength training.
Which split should you choose?
For general health, the U.S. National Academies set Acceptable Macronutrient Distribution Ranges (AMDR) for adults: protein 10–35% of calories, carbohydrate 45–65% and fat 20–35%. The "balanced" preset sits inside all three ranges. The other presets are popular for specific goals:
- High protein (30 / 40 / 30): common when losing fat or building muscle. Protein is the most filling macro and helps keep muscle during a calorie deficit.
- Low carb (30 / 20 / 50): some people find it easier to control appetite with fewer carbohydrates. It is outside the AMDR for carbs, which is fine for many healthy adults but worth discussing with a doctor if you take diabetes medication.
- Keto (20 / 5 / 75): keeps carbohydrate very low (usually under about 20–50 g per day) so the body produces ketones. It is restrictive and not suitable for everyone, including people who are pregnant or have certain kidney or liver conditions.
Research comparing diets shows that, when calories and protein are matched, low-fat and low-carb plans lead to similar fat loss over a year. The best split is the one you can keep to.
How much protein do you need?
The Recommended Dietary Allowance for adults is 0.8 g per kg of body weight per day, the amount that prevents deficiency in almost everyone. For active people the International Society of Sports Nutrition suggests 1.4–2.0 g/kg to support training and muscle gain, and somewhat more during an aggressive diet. A 70 kg person therefore needs about 56 g at minimum and roughly 100–140 g if training hard. If a percentage split gives far more or less than this, adjust the protein percentage.
Putting the numbers into practice
- Start with the calorie target. The split only divides calories; the total decides whether you gain or lose weight. Use the calorie calculator to set it.
- Spread protein through the day, for example 25–40 g in each of three or four meals.
- Be roughly right. Hitting each macro within about 5–10 g is plenty. Food labels and apps carry their own errors of 10% or more.
- Fibre counts within carbs on most labels. Aim for about 25–30 g of fibre a day from vegetables, fruit, legumes and whole grains.
- Track change over weeks. Weight and waist or body fat trends tell you whether the plan works better than any single day.
Common mistakes
- Percentages that do not add up to 100. The calculator warns you; a custom split must total 100%.
- Using 4 kcal per gram for fat. Fat has 9 kcal per gram, so 30% of calories from fat is far fewer grams than 30% from carbs.
- Confusing grams of food with grams of protein. 100 g of chicken breast contains about 30 g of protein, not 100 g.
General information only. People with kidney disease, diabetes, eating disorders or who are pregnant should get personal advice from a doctor or registered dietitian.
Frequently asked questions
How many grams of protein, carbs and fat should I eat on 2,000 calories?
With a 30/40/30 split: 150 g protein, 200 g carbs and about 67 g fat. With a balanced 20/50/30 split: 100 g protein, 250 g carbs and about 67 g fat.
How do I convert calories to grams of macros?
Multiply calories by the percentage, then divide by 4 for protein or carbs and by 9 for fat.
How much protein do I need per day?
At least 0.8 g per kg of body weight; about 1.4–2.0 g per kg if you train regularly or want to build muscle.
What is a good macro split for weight loss?
Any split works if calories are in a deficit, but a higher protein share (about 25–35%) helps keep you full and preserve muscle.
Sources
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005.
- Jäger R, et al. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr, 2017;14:20.
- Gardner CD, et al. Effect of low-fat vs low-carbohydrate diet on 12-month weight loss (DIETFITS randomized clinical trial). JAMA, 2018;319(7):667–679.
Last reviewed 14 October 2026. Results are estimates; see our disclaimer.