The short answer
Macros are the three main nutrients that supply calories: protein, carbohydrate and fat. This calculator estimates your daily calories, then splits them into grams of each macro using a preset such as balanced or higher protein. It shows how each split compares with general nutrient ranges and never uses calorie targets below safe limits.
Formulas and sources are named on this page. How we calculate.
How this is calculated
The macro calculator first finds a safe daily calorie target (the same way as our calorie calculator), then converts the share of calories assigned to each macro into grams.
Carbohydrate (g) = calories × carb % ÷ 4
Protein (g) = calories × protein % ÷ 4
Fat (g) = calories × fat % ÷ 9
The divisors are Atwater energy factors: about 4 kcal per gram of carbohydrate, 4 per gram of protein and 9 per gram of fat.
Worked example
A 2,000 kcal target on the balanced split (50% carbohydrate, 20% protein, 30% fat):
- Carbohydrate: 2,000 × 0.50 ÷ 4 = 250 g
- Protein: 2,000 × 0.20 ÷ 4 = 100 g
- Fat: 2,000 × 0.30 ÷ 9 = 66.7, shown as 67 g
Rounding to whole grams means the total is 2,003 kcal, which is close enough for a planning estimate.
How the splits compare with general ranges
The Institute of Medicine's Acceptable Macronutrient Distribution Ranges for adults are 45 to 65% of calories from carbohydrate, 20 to 35% from fat and 10 to 35% from protein. The Dietary Guidelines for Americans use the same ranges. The calculator flags any split outside them. The lower-carb preset is outside the carbohydrate and fat ranges, so it is best discussed with a dietitian first.
Protein per kilogram
The recommended dietary allowance for protein in healthy adults is 0.8 g per kg of body weight a day. The International Society of Sports Nutrition position stand discusses 1.4 to 2.0 g per kg for people who exercise regularly. The result shows your protein in g per kg so you can see where it sits. Higher intakes are not suitable for everyone, for example people with kidney disease.
Frequently asked questions
What are macros?
Macros, short for macronutrients, are the main nutrients that provide energy: protein, carbohydrate and fat. Counting them means tracking grams of each, rather than only total calories.
How much protein do I need each day?
The recommended dietary allowance for healthy adults is 0.8 g per kg of body weight. Position statements for people who exercise regularly discuss 1.4 to 2.0 g per kg. A dietitian can advise on the right amount for you, especially with a medical condition.
Which macro split should I choose?
Balanced is a good starting point because it sits inside the general ranges. Higher protein can help people who are very active, and higher carbohydrate can suit heavy endurance training. Lower-carb splits fall outside the general ranges, so check them with a dietitian.
Why do the macro calories not add up exactly?
Grams are rounded to whole numbers, and the 4, 4 and 9 kcal per gram figures are averages. Food labels can differ slightly, and fibre and alcohol are counted differently, so small gaps are normal.
Do I have to hit my macros exactly?
No. Food labels and databases are approximate, so the grams work best as a target to stay close to rather than a number to hit to the gram.
Is a macro calculator safe for everyone?
No. It is designed for healthy adults. If you are pregnant, breastfeeding, under 18, have a medical condition or have had an eating disorder, speak to a doctor or registered dietitian instead of relying on a calculator.
Disclaimer and editorial note
For information only, not medical advice. This calculator gives general estimates from the numbers you enter. It cannot diagnose, treat or prevent any condition and does not replace advice from a doctor, midwife, registered dietitian or other qualified professional who knows your history.
Written and maintained by the HealthFitnessHQ editorial team. We name the source of every formula and category used, and we review each calculator when guidance changes. Read how we work in our editorial policy and methodology.