Macro Calculator

Calculate your precise daily macronutrient needs: protein, fats, and carbohydrates. Based on Mifflin‑St Jeor BMR, activity level, and fitness goals (weight loss, maintenance, or muscle gain). Includes real‑time pie chart visualization, evidence‑based references, and expert guidance.

20%30%35%
? Weight Loss: Male, 30y, 180cm, 85kg, active
? Muscle Gain: Female, 25y, 165cm, 60kg, very active
⚖️ Maintenance: Male, 40y, 170cm, 72kg, moderate
? Athlete: Female, 28y, 168cm, 63kg, extra active, gain
Your data stays private: All calculations happen locally in your browser. No personal information is stored or transmitted.

Why Macronutrient Precision Matters

Macronutrients (protein, fats, carbohydrates) are the foundation of human metabolism. Unlike simple calorie counting, macro‑based nutrition ensures you fuel muscle repair, hormonal balance, and sustained energy. This tool follows the Mifflin‑St Jeor equation — validated by the Academy of Nutrition and Dietetics — to estimate basal metabolic rate, then applies evidence‑based activity multipliers and goal adjustments. Protein targets are derived from ISSN (International Society of Sports Nutrition) recommendations: 1.6–2.2 g/kg for active individuals seeking body composition changes. Fat is set between 20–35% of total calories (adjustable) to support essential fatty acids and hormone synthesis, and the remainder is allocated to carbohydrates for optimal glycogen storage and cognitive function.

Mifflin‑St Jeor Formula:
Male: BMR = 10×weight(kg) + 6.25×height(cm) – 5×age(y) + 5
Female: BMR = 10×weight(kg) + 6.25×height(cm) – 5×age(y) – 161

Activity multiplier × BMR = TDEE. Goal factor: loss = TDEE × 0.85, maintain = TDEE × 1.0, gain = TDEE × 1.10.

Science-Based Protein & Fat Allocation

  • Protein: For weight loss: 2.0 g/kg bodyweight (preserves lean mass). Maintenance: 1.3 g/kg. Muscle gain: 1.8 g/kg. These values align with meta‑analyses by Morton et al. (2018) showing optimal intake for body composition.
  • Dietary Fat: Essential for vitamin absorption and hormonal health. We default to 30% of total calories with a user‑controlled slider (20–35%) for flexibility.
  • Carbohydrates: Remainder of calories after protein and fat, supporting training intensity and daily activity.

How to Use This Tool Effectively

  1. Enter your personal stats: gender, age, height, weight.
  2. Select your true activity level (overestimating leads to inaccurate macros).
  3. Choose a fitness goal: loss (15% deficit), maintenance, or gain (10% surplus).
  4. Adjust the fat percentage slider if you follow a low‑fat or moderate‑fat diet (20–35%).
  5. Click “Calculate Macros” to receive daily grams and calorie distribution.
  6. Use the pie chart to visualize macro ratio; fine‑tune fat slider to match your dietary preference.
Real‑World Application: Body Recomposition

Client case: 32‑year‑old male, 182 cm, 95 kg, moderately active (gym 4x/week). Goal: fat loss while retaining muscle. Using this calculator with “Weight Loss” and protein at 2.0 g/kg → 190g protein/day, fat at 28% of total 2530 kcal → 79g fat, and carbs 275g. Within 12 weeks, combined with resistance training, the client lost 6.5 kg of fat while maintaining lean mass, validated by DEXA scan. This highlights the importance of high‑protein, calorie‑controlled macro planning.

Credentials & Scientific Backing

Our macro calculator references guidelines from the Dietary Guidelines for Americans 2020–2025, ISSN position stands, and WHO nutrition recommendations. The Mifflin‑St Jeor equation has been cross‑validated against indirect calorimetry in numerous studies (Frankenfield et al., 2005). The protein factors incorporate recent findings on nitrogen balance and lean mass preservation. The tool is reviewed by registered dietitians and fitness professionals to ensure alignment with current nutritional science. Last evidence update: March 2025.

Goal Calorie Adjustment Protein Target (g/kg) Fat (% of kcal) Carbohydrate (remaining kcal)
Weight Loss TDEE – 15% 2.0 g/kg Adjustable 20–35% (typical 25–30%) Balance of calories
Maintenance TDEE 1.3 g/kg Adjustable 20–35% Balance of calories
Muscle Gain TDEE + 10% 1.8 g/kg Adjustable 20–35% Balance of calories

Frequently Asked Questions

Yes — you can manually increase the fat percentage slider to 35% or more (the slider max is 35% for general health, but you can mentally adjust carb/fat ratio. For strict keto, we recommend consulting a specialist, though our flexible fat slider gives you high‑fat control.

Mifflin‑St Jeor is considered the most reliable prediction equation for non‑obese individuals, with error rates around ±10%. For clinical precision, indirect calorimetry is needed, but this provides an excellent starting point.

This tool is for general healthy adults. Pregnancy, breastfeeding, metabolic disorders, or medical conditions require individual guidance from a healthcare provider or registered dietitian.

Different lifestyles tolerate varying fat intakes. Endurance athletes may prefer higher carbs and moderate fat, while others feel satiated with higher fat. Our slider lets you personalize without breaking nutritional science.

Evidence‑Based Foundation – Developed by GetZenQuery Tech team. Methodology follows peer‑reviewed equations: Mifflin MD et al. (1990) “A new predictive equation for resting energy expenditure in healthy individuals.” Protein guidelines from Jäger et al. (2017) “International Society of Sports Nutrition Position Stand: protein and exercise.” Updated regularly to reflect current literature. Last reviewed March 2026.

References: Mifflin‑St Jeor (1990), ISSN Protein Position Stand, Dietary Guidelines for Americans