Energy & Macro Split

Curated by Vinod Kumar Jain & Amit Jain · All Frontier Global · free, no login

This applies the Mifflin-St Jeor equation — a published estimate of resting metabolic rate, written out in full below — multiplies it by an activity factor you choose, and splits the result into protein, fat and carbohydrate at ratios you set. These are population estimates, not dietary advice. Individual requirements vary substantially for reasons no equation captures. If your eating matters to your health, speak to a qualified professional rather than to a web page.

The equation, written out

• Mifflin-St Jeor resting metabolic rate, in kilocalories per day:
  male constant: RMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5
  female constant: RMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) − 161
• Daily energy estimate = RMR × the activity factor you selected.
• Macronutrient grams = daily energy × that macro’s percentage ÷ the energy per gram: protein 4 kcal/g, carbohydrate 4 kcal/g, fat 9 kcal/g.
• The three percentages should total 100; if they do not, the tool says so and shows what they do total rather than silently normalising them.

Read this before using the number

• These are population estimates, not dietary advice. The equation was derived to predict an average for a group. Individual requirements vary substantially with body composition, genetics, medication, health conditions, sleep and much else that no equation captures.
• Activity factors are coarse. The gap between two people who both describe themselves as “moderately active” can be several hundred kilocalories a day.
• The equation uses a sex-based constant because that is how it was published. It is a statistical constant fitted to study populations, not a statement about any individual, and it will fit some people poorly.
• Consult a qualified professional — a registered dietitian or your doctor — before acting on any of this, and particularly if you are pregnant or breastfeeding, are managing a health condition, take medication that affects appetite or metabolism, are under 18, or have any history of disordered eating. Nothing here is suitable for those situations.
• Nothing you enter is stored or sent. Broader wellbeing writing lives on AFG Wellness.

Sources

The resting metabolic rate equation is the one published by Mifflin, St Jeor and colleagues in the American Journal of Clinical Nutrition in 1990, reproduced above as an equation and attributed. Activity multipliers are the conventional set used alongside it and are approximations rather than measurements. The energy densities used for macronutrients — 4, 4 and 9 kilocalories per gram — are the standard convention. Broader wellbeing writing sits on AFG Wellness, which is editorial rather than clinical. No dietary guideline, target or recommendation is embedded, and no health data is fetched or stored.

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