Which equation should I use: Mifflin–St Jeor or Katch–McArdle?

Use Mifflin–St Jeor if you do not know your body fat percentage. Use Katch–McArdle if you have a reasonably accurate body fat estimate, as it accounts for lean body mass.

How accurate are activity multipliers?

They are averages. Individual variability can be large. Use them as a starting point and adjust based on your real-world weight trends over 2–4 weeks.

What protein intake should I choose?

A common range is 1.6–2.2 g/kg of body weight (or lean mass). Start around 1.8 g/kg and adjust based on satiety, training load, and preferences.

Can I calculate macros for keto or low-carb?

Yes. Increase fat percent or set fat as grams per kg, and allow carbs to be the remainder. Ensure adequate protein and fiber.

Is this medical advice?

No. This calculator is for educational purposes and general guidance. Consult a qualified professional for personalized medical or nutrition advice.

How do I improve accuracy over time?

Track your intake and body weight for 2–4 weeks. If weight changes faster or slower than planned, adjust daily calories by 5–10% and re-evaluate.

Macro Calculator

This interactive macro calculator estimates your daily energy needs (TDEE) and translates them into practical protein, fat, and carbohydrate targets. It’s built for anyone optimizing nutrition for fat loss, muscle gain, or maintenance, using peer‑reviewed equations and accessible, mobile‑first design.

Data Source and Methodology

Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition 1990;51(2):241–247. DOI
Katch VL, McArdle WD. Nutrition, Weight Control, and Exercise. Houghton Mifflin; 1993. (Katch–McArdle BMR: BMR = 370 + 21.6 × LBM[kg])
Activity multipliers adapted from FAO/WHO/UNU Expert Consultation on Human Energy Requirements (2001) and common sports nutrition practice.
Protein guidance synthesized from Morton RW et al., Br J Sports Med. 2018;52:376–384. DOI

Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

The Formula Explained

BMR (Mifflin–St Jeor):

For men: \( \mathrm{BMR} = 10W + 6.25H - 5A + 5 \)

For women: \( \mathrm{BMR} = 10W + 6.25H - 5A - 161 \)

BMR (Katch–McArdle): \( \mathrm{BMR} = 370 + 21.6 \times \mathrm{LBM} \)

where \( \mathrm{LBM} = W \times (1 - \frac{\%BF}{100}) \)

Total Daily Energy Expenditure (TDEE): \( \mathrm{TDEE} = \mathrm{BMR} \times \mathrm{Activity} \)

Goal calories: \( \mathrm{Calories}_{target} = \mathrm{TDEE} \times (1 + r) \) where r is goal rate (e.g., −0.20)

Macros:

\( P_{g} = p \times \text{kg basis} \), \( F_{g} = \begin{cases} \frac{f\% \times \mathrm{Calories}}{9} & (\%) \\ f_{kg}\times \text{kg basis} & (\mathrm{g/kg})\end{cases} \)

\( C_{g} = \frac{\mathrm{Calories} - 4P_{g} - 9F_{g}}{4} \)

Glossary of Variables

W: Body weight in kilograms (kg).
H: Height in centimeters (cm).
A: Age in years.
%BF: Body fat percentage.
LBM: Lean body mass (kg).
BMR: Basal Metabolic Rate (kcal/day).
TDEE: Total Daily Energy Expenditure (kcal/day).
r: Goal rate as a fraction (e.g., −0.2 = 20% deficit).
P_g, F_g, C_g: Protein, fat, carbohydrate grams per day.
p: Protein in g/kg (basis: body weight or lean mass).
f%: Fat as percent of calories. f_kg: Fat in g/kg.

How It Works: A Step-by-Step Example

Inputs: Male, 30 years, 180 cm, 80 kg, 15% body fat, activity 1.55, goal −20%, protein 1.8 g/kg (total body weight), fat 25% calories.

BMR (MSJ): 10×80 + 6.25×180 − 5×30 + 5 = 1780 kcal/day.
TDEE: 1780 × 1.55 = 2759 kcal/day.
Target calories: 2759 × (1 − 0.20) = 2207 kcal/day.
Protein: 1.8 × 80 = 144 g (576 kcal).
Fat: 25% × 2207 = 551.8 kcal → 61.3 g.
Carbs: (2207 − 576 − 551.8) / 4 = 269.8 g.

Frequently Asked Questions (FAQ)

Do I need my body fat percentage?

No. If you don’t know it, use Mifflin–St Jeor. If you have a good estimate, Katch–McArdle can personalize BMR via lean mass.

What if my carbs calculate as negative?

Reduce protein or fat targets, or increase total calories. Very high protein plus high fat at low calories can leave no room for carbs.

How fast should I lose or gain?

Common guidance: lose 0.25–1.0% body weight per week; gain 0.25–0.5% to minimize fat gain. Adjust the goal percentage accordingly.

Are activity multipliers accurate for athletes?

They are averages. Endurance or physically demanding jobs may require higher multipliers. Use weight trends to calibrate.

Should protein be based on lean mass or total weight?

If body fat is high or known, lean-mass basis can be more appropriate. Otherwise, total body weight basis is fine.

Is fiber included?

This calculator targets total carbohydrates. Aim for 25–35 g/day of fiber from whole foods for health and satiety.

Can I export or print results?

Copy the results into your notes or a meal-planning tool. A print-friendly layout is supported by your browser.

Strumento sviluppato da Ugo Candido,. Contenuti verificati da,.
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