The Macronutrient Calculator estimates your basal metabolic rate, daily energy expenditure, target calories for your goal, and the protein, carbohydrate, and fat grams that target splits into, in metric units. Enter sex, age, weight in kilograms, height in centimetres, activity level, goal, and a macro split style.
How It Works
BMR uses the Mifflin-St Jeor equation; multiplying by the activity factor (1.2 sedentary to 1.9 very active) gives TDEE. The goal adjusts the target: minus 500 kcal to lose, plus 500 to gain, unchanged to maintain. Two safety floors then apply: the target is never set below 1,500 kcal for men or 1,200 kcal for women. Finally the chosen split divides the calories, balanced at 30% protein, 40% carbohydrate, 30% fat; low carb at 40/20/40; and high protein at 40/30/30, with grams at 4 kcal per gram for protein and carbohydrate and 9 for fat.
Parameters
| Input | Required | Meaning | |---|---|---| | Sex, age | Yes | Age 15 to 120 | | Weight and height | Yes | Kilograms (30-300) and centimetres (100-250) | | Activity level | Yes | Sedentary through very active | | Goal | Yes | Lose, maintain, or gain | | Split | Yes | Balanced, low carb, or high protein |
Worked example
A 28-year-old woman, 65 kg, 165 cm: BMR = 650 + 1,031 - 140 - 161 = 1,380 kcal. At light activity (x1.375), TDEE is 1,898 kcal. For the lose goal the target is 1,398 kcal, comfortably above the 1,200 floor. On the balanced split that is about 105 g protein (30%), 140 g carbohydrate (40%), and 47 g fat (30%). Switch her to the high-protein split and protein rises to about 140 g while carbohydrate falls to about 105 g and fat stays near 47 g, illustrating exactly what a split changes: the protein-carbohydrate balance at fixed calories and roughly fixed fat in this preset family.
The safety floors, explained
Aggressive calculators happily output 900-kcal targets that no one should follow. The floors here (1,500 men, 1,200 women) are the levels below which unsupervised dieting risks nutrient inadequacy and lean-mass loss; if your computed target hits the floor, the intended deficit has been softened deliberately, and progress will be slower than the nominal 500-kcal pace. Persistent need for a larger deficit is a clinician conversation, not a bigger subtraction. The same caution applies in reverse for gaining: the +500 surplus is a starting point, and if weight races upward, fat, not muscle, is making the pace.
How this differs from the Macro Calculator on this site
The two tools share an engine family but differ in inputs and presets: this one is metric-only with three splits and explicit calorie floors, while the Macro Calculator adds imperial units, finer goal steps (a 200-kcal lean bulk), and a low-fat preset. If both are run on the same person with matching settings, results should agree closely; the differences are in the edges described above, and either is a valid starting hypothesis to calibrate against two to three weeks of real weight trend.
Limitations
Predictive equations carry roughly plus or minus 10% individual error, activity selection is approximate, and the splits are presets rather than individualized prescriptions (protein by body weight, for example, is not how these percentages are derived). The calculator does not consider pregnancy, eating-disorder history, metabolic disease, or medication effects. Treat the output as a testable starting target and adjust by observed trend.
Frequently Asked Questions
Why did my target stop at 1,200 or 1,500 kcal?
You hit the safety floor: your TDEE minus 500 fell below the minimum the calculator will prescribe. The deficit is intentionally capped; discuss anything more aggressive with a clinician.
Which split should I choose?
Balanced for general health and training, high protein when cutting or prioritizing muscle retention, low carb if you prefer fat-rich foods and steadier appetite. At equal calories, adherence matters more than the split.
How soon should the target change my weight?
The 500-kcal adjustment approximates half a kilogram per week. Judge after two to three weeks of consistent intake, and adjust by 100 to 200 kcal based on the trend rather than daily fluctuations.