Macro Calculator

How to use the macro calculator

1. Enter your Daily calories (kcal). If you do not know them, fill in the optional section at the bottom (units, sex, age, height, weight and activity level) and press Use my maintenance calories: the estimate is copied into the calories field.
2. Choose a Split: Balanced (20 % protein, 50 % carbs, 30 % fat), Higher protein (30/40/30) or Lower carb (30/35/35).
3. Adjust the Protein, Carbohydrates and Fat percentages if you want. The split switches to Custom as soon as you edit one; the three values must add up to 100 %.
4. Read the table: grams per day, kcal per day and the reference range for each macronutrient. When a weight is filled in, the tool also shows your protein intake in grams per kilogram of body weight.

The table updates as you type. Nothing leaves your browser.

How the calculation works

Each macronutrient supplies a known amount of energy per gram, using the Atwater general factors: 4 kcal per gram of protein, 4 kcal per gram of carbohydrate and 9 kcal per gram of fat. The tool multiplies your calories by each percentage, then divides by the energy per gram:

grams = calories × percentage ÷ 100 ÷ kcal per gram

Example with 2,000 kcal and the balanced split:

• protein: 2,000 × 20 % = 400 kcal ÷ 4 = 100 g;
• carbohydrates: 2,000 × 50 % = 1,000 kcal ÷ 4 = 250 g;
• fat: 2,000 × 30 % = 600 kcal ÷ 9 = 67 g.

The optional estimate uses the Mifflin-St Jeor equation (Mifflin et al., American Journal of Clinical Nutrition, 1990) multiplied by a standard activity factor from 1.2 (sedentary) to 1.9 (extra active). It gives maintenance calories, not a weight-loss or weight-gain target.

Reference ranges (AMDR)

The US National Academies’ Institute of Medicine set Acceptable Macronutrient Distribution Ranges for adults in its Dietary Reference Intakes report (2005): 10–35 % of energy from protein, 45–65 % from carbohydrates and 20–35 % from fat. Within these ranges, an adequate intake of essential nutrients is achievable and chronic disease risk is lower. The balanced preset sits inside all three ranges. The higher-protein preset is still inside them. The lower-carb preset puts carbohydrates below 45 %, which the table flags as outside the reference range: it is a common choice, but not a default recommendation.

For protein, the Recommended Dietary Allowance is 0.8 g per kg of body weight per day for healthy adults. Active people and older adults often benefit from more, and the grams-per-kilogram line helps you compare.

Limits and good practice

A macro split describes quantities, not food quality. The same grams of carbohydrate can come from whole grains, fruit and legumes or from sugary drinks, with very different effects on health. Fibre, vitamins, minerals and the type of fat matter as much as the totals.

The calorie estimate is approximate and individual needs vary. Very low calorie intakes (below about 1,200 kcal a day) make it hard to meet nutrient needs, so the tool shows a warning. Kidney disease, diabetes, pregnancy, eating disorders and many other situations call for personalised advice: talk to a registered dietitian or your doctor before making big changes to your diet.