What are macronutrients?
Macronutrients — protein, carbohydrates and fat — are the three nutrients that provide energy. Protein and carbs deliver about 4 kcal per gram, fat about 9. Your calorie total decides whether you gain or lose weight, but the split between these three is what shapes the result: enough protein protects muscle, carbs fuel training, and fat supports hormones. A macro target gives you a concrete plan instead of a vague calorie number.
Macros for losing weight
To lose fat you eat fewer calories than you burn. We apply a moderate deficit of around 500 kcal, which supports steady fat loss of roughly half a kilo per week. Protein is deliberately high while cutting — about 2.5 g per kg of lean body mass — because it preserves muscle in a deficit and keeps you full. Carbs and fat fill the rest, so you still have energy to train hard and recover.
Macros for building muscle
Building muscle needs a calorie surplus — a little more than you burn. We add a moderate surplus so you gain lean mass without unnecessary fat. Protein sits around 2.0 g per kg of bodyweight to supply the building blocks, while carbohydrates take a larger share to fuel heavy training and recovery. Progress is slow by nature: even in a good phase, expect to add muscle over months, not weeks.
Macros across different diets
Your diet changes the carb-to-fat balance, not the protein target. A balanced omnivore or pescatarian split leans slightly toward carbohydrates, while a vegetarian or vegan diet shifts a little further toward them. We always protect a minimum fat intake of 0.8 g per kg for hormonal health — especially important for women in a deficit. Whatever you eat, the calculator keeps your protein where it needs to be.
A worked example
Take a woman, 32, 68 kg, 170 cm, mostly walking during the day and training three times a week, aiming to lose weight on an omnivore diet. Her basal rate is about 1,422 kcal; with activity and training her total burn is roughly 2,350 kcal. A 500 kcal deficit lands her near 1,850 kcal a day — split into about 119 g protein, 206 g carbs and 61 g fat.
These results are science-based estimates for healthy adults and are a starting point, not individual medical or nutritional advice. If you are pregnant, have a medical condition or specific dietary needs, talk to a doctor or registered dietitian.
Sources
- Mifflin MD, St Jeor ST, et al. (1990) — A new predictive equation for resting energy expenditure in healthy individuals.
- Helms ER, et al. (2014) — Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation.
- DGE — German Nutrition Society reference values for nutrient intake.
Last reviewed: July 2026.
Founder & Software Developer
Developing fitness software since 2018. Personal training experience: 15 years of strength training.