What macronutrients are
Macronutrients, or "macros", are the three main components of food that supply energy to the body: protein, carbohydrates and fat. While vitamins and minerals (micronutrients) are needed in small amounts, macros are needed in large amounts (grams) every day.
Each macro plays an essential role:
• Protein: the building blocks of the body. Essential for building and repairing tissue (including muscle), producing enzymes and hormones, and supporting the immune system. (Provides ~4 kcal per gram.) • Fat (lipids): fundamental for hormone health, absorbing fat-soluble vitamins (A, D, E and K), protecting organs and storing long-term energy. (Provides ~9 kcal per gram.) • Carbohydrates: the body's and the brain's preferred and fastest source of energy. (Provides ~4 kcal per gram.)
How to calculate your macros
The macro split in this calculator follows an evidence-based standard for optimizing body composition (losing fat while keeping muscle, or gaining lean mass):
1. First we set total calories based on your BMR, activity factor and goal (lose, maintain or gain). 2. Protein: fixed at ~1.8 grams per kilogram of body weight. Several studies consider this the ideal amount for maximizing protein synthesis, whether you are in a calorie deficit or building muscle. 3. Fat: we reserve around 25% of daily calories for fat. That is enough to keep hormone production healthy. 4. Carbohydrates: the remaining calories go to carbs. They supply the energy you need for training and daily life.
Protein, carbs and fat: how much of each
While the calculator gives you an excellent starting point, the ideal split can vary depending on your food preferences, genetics and type of training.
Endurance athletes (running, cycling) may need a higher proportion of carbohydrates, slightly reducing fat or protein. People with insulin resistance, or those who simply prefer higher-fat diets, can lower carbs and raise fat.
The main rule is: hit your calorie target and, to improve body composition, hit your protein target. The exact ratio between fat and carbs is less rigid and can be adapted to whatever you feel best following.
How macros change with your goal
The beauty of calculating macros is the flexibility. Your body weight dictates protein, but your total calories — which dictate carbs and fat — change with your goal.
• Losing fat: protein stays high (crucial for not losing muscle mass), while carbs and fat come down to create the calorie deficit. • Building muscle: you eat more calories overall. Protein stays sufficient (1.8 to 2.0 g/kg), but carbs increase significantly to fuel hard training and build new tissue.
Frequently asked questions
- Do I have to hit my macros to the gram every single day?
- No. Being perfectly exact is practically impossible. Focus on hitting your total calories within a margin (± 5–10%) and eating enough protein. If one day you eat slightly more carbs and slightly less fat, that is fine, as long as calories stay within range.
- Won't eating fat make me gain weight?
- No. What causes weight gain is a total calorie surplus. Dietary fats (olive oil, avocado, nuts) are essential for your health and for producing hormones such as testosterone. The only thing to watch is the amount, since fat carries more than twice the calories (9 kcal/g) of protein and carbs (4 kcal/g).
- Can I cut carbohydrates completely?
- The human body can survive without carbohydrates (through a process called ketogenesis), but most people feel much better, have more energy in training and stick to their diet more easily when they eat carbs in reasonable amounts. Cutting them entirely is unnecessary for weight loss.
- Which macro matters most for strength training?
- Protein. Without it, the body cannot repair the microdamage caused by training and build new muscle fibers. That said, carbohydrates come second, since they supply the fuel you need to train hard.
- How do I track macros practically day to day?
- By putting technology to work. With Nutricalor, instead of weighing everything on a scale and logging every gram, you simply photograph your plate. The AI estimates the macros from the food that is actually there, which makes tracking easy and sustainable over the long term.
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