Macros are a division of a calorie total, so the total has to come first. The most accurate widely used prediction equation for resting metabolic rate is Mifflin-St Jeor, which outperformed the older Harris-Benedict equation in validation studies:
BMR = 10 × kg + 6.25 × cm − 5 × age + 5BMR = 10 × kg + 6.25 × cm − 5 × age − 161Then multiply by an activity factor to get total daily energy expenditure: 1.2 sedentary, 1.375 light activity, 1.55 moderate, 1.725 very active, 1.9 athlete or heavy physical job.
A 30-year-old man, 70 kg, 175 cm, training three or four times a week.
BMR = 700 + 1,093.75 − 150 + 5 = 1,649 calories. Applying the moderate factor of 1.55 gives a maintenance figure of 2,556 calories a day.
Now the split, using the ranges with the strongest support in the resistance-training literature:
| Macro | Rule used | Grams | Calories |
|---|---|---|---|
| Protein | 1.8 g per kg | 126 g | 504 |
| Fat | 0.8 g per kg | 56 g | 504 |
| Carbohydrate | Remainder | 387 g | 1,548 |
| Total | 2,556 |
Protein and carbohydrate supply 4 calories per gram; fat supplies 9. That asymmetry is why fat grams look small next to carb grams for the same energy.
Protein and fat have floors that carbohydrate does not. Protein preserves lean mass and is the most satiating macro; dietary fat is required for fat-soluble vitamin absorption and hormone production. Carbohydrate is the flexible remainder — useful for training performance, but not essential in the same way.
A deficit of 15 to 25% of maintenance is a sustainable rate for fat loss — for our example, 2,556 less 20% is about 2,045 calories. Notice what happens to the split: protein goes up to 2.0 g per kg (140 g, 560 cal) to protect muscle, fat comes down slightly to 0.7 g per kg (49 g, 441 cal), and carbohydrate absorbs the whole cut, dropping from 387 g to 261 g. The deficit is paid for almost entirely out of carbs.
For a bulk, a surplus of 10 to 15% — around 2,800 calories here — is enough. Larger surpluses add fat faster than they add muscle, because the rate at which you can build lean tissue is capped by physiology, not by intake.
Mifflin-St Jeor predicts the population average for your height, weight, age and sex. Individual metabolic rate varies by roughly plus or minus 10%, and the activity multiplier is the crudest part of the whole calculation — people routinely misjudge their own category. So treat the output as a two-week starting hypothesis, not a fact:
The equation also does not apply cleanly to people with very high or very low body fat, to children and adolescents, during pregnancy or breastfeeding, or to anyone with a thyroid or metabolic condition. This is general information, not medical or dietary advice — if you have a diagnosed condition or a history of disordered eating, work with a professional rather than a calculator.
No. Weekly totals matter far more than daily ones, and being within 10 grams is fine. Protein is the one worth being consistent about.
Very little for body composition, once daily totals are equal. Spreading protein over three or four meals is marginally better than one large serving for muscle protein synthesis, and eating carbohydrate around training can help performance. Beyond that, choose the schedule you can keep.
Lean mass is more accurate if you know it, especially at higher body fat percentages, where total weight overstates need. Most people do not have a reliable lean mass figure, so total weight with a mid-range factor is the practical choice.
No. Height, weight, age and activity are used only in your browser to produce the numbers, and nothing is uploaded or stored.
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