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CALCULATOR · Health

Macro Calculator

Estimate your BMR and TDEE with the Mifflin–St Jeor equation and split your daily calories into protein, carbohydrate and fat targets in grams.

Show formula
BMR via Mifflin–St Jeor (1990); TDEE = BMR × activity factor (1.2–1.9); calories −500 kcal to lose, +500 kcal to gain. Macro split: 30% protein / 30% fat / 40% carbs of daily calories, converted to grams via Atwater factors (4 / 9 / 4 kcal/g).

Method reviewed:Mifflin et al. (1990) and Harris–Benedict activity multipliers reviewed against the 2021 Dietary Guidelines macronutrient AMDRs.

Inputs

30
65
165

Light exercise 1–3 days a week.

Result

Calories

Calories: 1,884

Maintain weight

BMR
1,370
TDEE
1,884
Activity factor
1.38

Lightly active

1,884MACRO SPLIT
  • Protein · 141 g56530.0%
  • Fat · 63 g56530.0%
  • Carbs · 189 g75440.0%

Macro split

  • Protein141 g · 565
  • Fat63 g · 565
  • Carbs189 g · 754
Show formula
BMR (Mifflin–St Jeor) · TDEE = BMR · activity factor. Protein 30% / Fat 30% / Carbs 40% of calories; grams via Atwater 4 / 9 / 4.

A planning estimate, not medical or nutritional advice. Diabetes, kidney disease, metabolic conditions, or active medical treatment — please consult a registered dietitian.

How the macro calculation works

  1. Enter age, sex, height, weight and activity level. The same Mifflin–St Jeor equation the Calorie Calculator uses is applied here, so the two pages always agree.
  2. Pick a goal — lose, maintain or gain. The calorie target moves 500 kcal down or up and never goes below a safe minimum.
  3. Read the per-macro targets in both calories and grams, and the BMR / TDEE figures that produced them.

Frequently asked questions

Why 30 / 30 / 40 for protein, fat and carbs?

It is one widely used starting split for general fitness — not a universal rule. Active people often push protein higher (35–40%), endurance athletes push carbs higher (45–55%), and therapeutic diets push fat higher (ketogenic). The calculator uses the common 30/30/40 split; for another ratio, apply your own percentages to the calorie target it gives.

Is the macro calculator the same as the calorie calculator?

The BMR and TDEE math are identical — both use Mifflin–St Jeor and the same activity factors — so the underlying energy figure cannot drift between the two pages. The macro page adds a protein / fat / carb split on top.

Is this medical advice?

No. It is a planning estimate. People with diabetes, kidney disease, metabolic conditions or active medical treatment should consult a registered dietitian.

Examples

30-year-old female, 65 kg, 165 cm, lightly active, maintain.
BMR ≈ 1,370 kcal. With a 1.375 activity factor, TDEE ≈ 1,884 kcal. Macros at 30/30/40 split: 141 g protein, 63 g fat, 189 g carbs.
Same person, goal: lose 0.5 kg a week.
Calories drop to 1,384 (TDEE − 500), still above the 1,200 kcal safe floor. Macros: 104 g protein, 46 g fat, 139 g carbs.

Macro vs Calorie Calculator

Use Calorie for a calorie target alone. Use Macro when you also want the split into protein, carbs and fat grams.

  • Calorie Calculator — You only need a daily calorie target and want the activity factor and goal arithmetic laid out separately.
  • BMI Calculator — You want a quick body-composition context before deciding on a calorie target.

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