How Do I Calculate Macros for Weight Loss

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Macro Calculator for Weight Loss

Enter your details to calculate your recommended daily macronutrient intake.

Male Female
Sedentary (little to no exercise) Lightly Active (light exercise/sports 1-3 days/week) Moderately Active (moderate exercise/sports 3-5 days/week) Very Active (hard exercise/sports 6-7 days a week) Extra Active (very hard exercise, physical job or training)
Slow & Sustainable (0.25 kg/week) Moderate (0.5 kg/week) Aggressive (0.75 kg/week)

Your Daily Macro Targets for Weight Loss

Calories: kcal

Protein: g

Fat: g

Carbohydrates: g

Understanding Macronutrient Calculation for Weight Loss

Calculating your macronutrient (macros) targets is a cornerstone of effective and sustainable weight loss. Macronutrients are the nutrients your body needs in large amounts: carbohydrates, proteins, and fats. By adjusting the balance and total amount of these, you can create a calorie deficit necessary for losing weight while ensuring your body receives the fuel and building blocks it needs.

1. Calculating Basal Metabolic Rate (BMR)

Your BMR is the number of calories your body burns at rest to maintain basic functions like breathing, circulation, and cell production. We commonly use the Mifflin-St Jeor equation, which is considered more accurate than older formulas:

  • For Men: BMR = (10 * weight in kg) + (6.25 * height in cm) - (5 * age in years) + 5
  • For Women: BMR = (10 * weight in kg) + (6.25 * height in cm) - (5 * age in years) - 161

2. Calculating Total Daily Energy Expenditure (TDEE)

Your TDEE is the total number of calories you burn in a day, including your BMR and your activity level. We estimate this by multiplying your BMR by an activity factor:

  • Sedentary: BMR x 1.2
  • Lightly Active: BMR x 1.375
  • Moderately Active: BMR x 1.55
  • Very Active: BMR x 1.725
  • Extra Active: BMR x 1.9

The calculator uses your selected activity level to determine your TDEE.

3. Determining Calorie Deficit for Weight Loss

To lose weight, you need to consume fewer calories than your TDEE, creating a calorie deficit. A deficit of approximately 3500 calories equates to about 0.5 kg (1 lb) of fat loss. For sustainable weight loss, a deficit of 500-750 calories per day is generally recommended. This calculator subtracts a deficit based on your chosen weekly goal:

  • 0.25 kg/week ~ 250 calorie deficit
  • 0.5 kg/week ~ 500 calorie deficit
  • 0.75 kg/week ~ 750 calorie deficit

Target Calories = TDEE - Calorie Deficit

4. Setting Macronutrient Ratios

Once you have your target daily calorie intake, you can distribute them among protein, carbohydrates, and fats. For weight loss, a common and effective approach prioritizes protein to help preserve muscle mass and promote satiety, while moderating carbs and fats.

  • Protein: Crucial for muscle repair and growth, and helps you feel full. A common recommendation is 1.6 to 2.2 grams per kilogram of body weight. For weight loss, aiming on the higher end is often beneficial.
    Protein (grams) = Body Weight (kg) * 1.8 (Adjustable based on user preference, this calculator uses a simplified approach based on percentage for demonstration.)
  • Fat: Essential for hormone production and nutrient absorption. A minimum of 0.5 grams per kilogram of body weight is recommended, often making up around 20-30% of total calories.
    Fat (grams) = (Target Calories * 0.25) / 9 (Using 25% of target calories)
  • Carbohydrates: Provide the body's primary source of energy. The remaining calories after protein and fat are allocated to carbohydrates.
    Carbohydrates (grams) = (Target Calories - (Protein grams * 4) - (Fat grams * 9)) / 4

Note: 1 gram of protein provides 4 calories, 1 gram of carbohydrates provides 4 calories, and 1 gram of fat provides 9 calories.

Example Calculation

Let's calculate for a 35-year-old female, weighing 70 kg, 165 cm tall, who is moderately active and aiming to lose 0.5 kg per week.

  1. BMR: (10 * 70) + (6.25 * 165) – (5 * 35) – 161 = 700 + 1031.25 – 175 – 161 = 1395.25 kcal
  2. TDEE: 1395.25 * 1.55 (Moderately Active) = 2162.64 kcal
  3. Calorie Deficit: 500 kcal (for 0.5 kg/week loss)
  4. Target Calories: 2162.64 – 500 = 1662.64 kcal. Let's round to 1660 kcal.
  5. Macro Split:
    • Protein: Using 1.8g/kg => 70 kg * 1.8 g/kg = 126 g. (126g * 4 kcal/g = 504 kcal)
    • Fat: Let's allocate 25% of target calories => (1660 kcal * 0.25) / 9 kcal/g = 46 g. (46g * 9 kcal/g = 414 kcal)
    • Carbohydrates: Remaining calories => (1660 – 504 – 414) / 4 kcal/g = 742 / 4 = 185.5 g. Let's round to 186 g.

Result: Approximately 1660 kcal, 126g Protein, 46g Fat, 186g Carbohydrates.

Disclaimer: This calculator provides estimations. Consult with a healthcare professional or registered dietitian for personalized advice.

function calculateMacros() { var gender = document.getElementById("gender").value; var age = parseFloat(document.getElementById("age").value); var weight = parseFloat(document.getElementById("weight").value); var height = parseFloat(document.getElementById("height").value); var activityLevel = parseFloat(document.getElementById("activityLevel").value); var goal = parseFloat(document.getElementById("goal").value); var resultDiv = document.getElementById("result"); var targetCaloriesSpan = document.getElementById("targetCalories"); var targetProteinSpan = document.getElementById("targetProtein"); var targetFatSpan = document.getElementById("targetFat"); var targetCarbsSpan = document.getElementById("targetCarbs"); // Input validation if (isNaN(age) || isNaN(weight) || isNaN(height) || weight <= 0 || height <= 0 || age 7700 * 0.25 = 1925 kcal/week => ~275 kcal/day deficit // 0.5 kg/week => 7700 * 0.5 = 3850 kcal/week => ~550 kcal/day deficit // 0.75 kg/week => 7700 * 0.75 = 5775 kcal/week => ~825 kcal/day deficit var calorieDeficit = 0; if (goal === 0.25) { calorieDeficit = 275; } else if (goal === 0.5) { calorieDeficit = 550; } else if (goal === 0.75) { calorieDeficit = 825; } var targetCalories = tdee – calorieDeficit; // Ensure target calories are not excessively low (e.g., below 1200 for women, 1500 for men) var minCalories = (gender === "female") ? 1200 : 1500; if (targetCalories targetCalories) { // Rebalance: Reduce fat slightly or adjust protein percentage if too high // For simplicity here, we'll cap fat and var carbs be minimal if needed fatTargetCalories = Math.max(targetCalories * 0.20, weight * 0.5 * 9); // Ensure minimum fat intake fatTargetGrams = fatTargetCalories / 9; carbTargetCalories = targetCalories – proteinCalories – fatTargetCalories; carbTargetGrams = carbTargetCalories / 4; } // Ensure carbs are not negative if (carbTargetGrams < 0) { carbTargetGrams = 0; // If carbs are zero, try to slightly reduce protein/fat if possible, or warn user var remainingCalories = targetCalories – (proteinTargetGrams * 4) – (fatTargetGrams * 9); if (remainingCalories < 0) { // Extremely low calorie target, try to reduce fat first var reductionNeeded = Math.abs(remainingCalories); var fatReductionGrams = Math.min(fatTargetGrams – (weight * 0.5), reductionNeeded / 9); fatTargetGrams -= fatReductionGrams; // Recalculate carbs just in case, should be very close to 0 carbTargetGrams = (targetCalories – (proteinTargetGrams * 4) – (fatTargetGrams * 9)) / 4; } } // Rounding for display var roundedTargetCalories = Math.round(targetCalories); var roundedTargetProtein = Math.round(proteinTargetGrams); var roundedTargetFat = Math.round(fatTargetGrams); var roundedTargetCarbs = Math.round(carbTargetGrams); targetCaloriesSpan.textContent = roundedTargetCalories; targetProteinSpan.textContent = roundedTargetProtein; targetFatSpan.textContent = roundedTargetFat; targetCarbsSpan.textContent = roundedTargetCarbs; resultDiv.style.display = "block"; }

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