Data Source and Methodology

This calculator provides a precise estimate of your daily caloric and macronutrient needs based on the industry-standard Mifflin-St Jeor Equation for calculating Basal Metabolic Rate (BMR).

All calculations for BMR and TDEE (Total Daily Energy Expenditure) are based strictly on the formulas and activity multipliers derived from this and related metabolic research. Your calorie target is then adjusted based on your stated goal.

The Formulas Explained

Your calculation is a three-step process: 1. **Calculate Basal Metabolic Rate (BMR):** The calories your body burns at complete rest. 2. **Calculate TDEE:** Your BMR is multiplied by an activity factor to find your total daily energy expenditure (maintenance calories). 3. **Apply Goal:** Your TDEE is adjusted (e.g., -500 calories) to create a target for weight loss or gain.

1. BMR (Mifflin-St Jeor Equation)

The formula differs slightly for biological males and females.

For Men:
$BMR = (10 \times \text{weight in kg}) + (6.25 \times \text{height in cm}) - (5 \times \text{age in years}) + 5$

For Women:
$BMR = (10 \times \text{weight in kg}) + (6.25 \times \text{height in cm}) - (5 \times \text{age in years}) - 161$

2. TDEE (Total Daily Energy Expenditure)

This is your BMR multiplied by your chosen activity level.

$TDEE = BMR \times \text{Activity Multiplier}$
  • Sedentary: 1.2
  • Lightly Active: 1.375
  • Moderately Active: 1.55
  • Very Active: 1.725
  • Extra Active: 1.9

3. Macronutrient Split

Your target calories are then divided into protein, carbohydrates, and fats based on your preference.

  • 1 gram of Protein = 4 calories
  • 1 gram of Carbohydrate = 4 calories
  • 1 gram of Fat = 9 calories

Glossary of Variables

Basal Metabolic Rate (BMR)
The minimum number of calories your body needs to perform basic, life-sustaining functions at rest.
Total Daily Energy Expenditure (TDEE)
Your BMR plus all the calories you burn from physical activity, digestion, and daily tasks. This is also known as your "maintenance calories"—the amount you need to eat to stay the same weight.
Target Calories
Your TDEE adjusted to meet your goal. To lose 0.5 kg (1.1 lbs) per week, this number is typically your TDEE minus 500 calories per day.
Macronutrients (Macros)
The three main nutrient categories: Protein, Carbohydrates, and Fats. Your meal plan is built by consuming foods that meet these daily gram targets.

How It Works: A Step-by-Step Example

Let's see how the calculator works for a hypothetical person: "Sarah".

  • Inputs:
    • Age: 30
    • Sex: Female
    • Weight: 70 kg (154 lbs)
    • Height: 165 cm (5' 5")
    • Activity: Lightly Active (exercises 2 days/week)
    • Goal: Lose 0.5 kg (1.1 lbs) per week
    • Preference: Balanced Macros

Step 1: Calculate BMR

$BMR = (10 \times 70) + (6.25 \times 165) - (5 \times 30) - 161$
$BMR = 700 + 1031.25 - 150 - 161 = \textbf{1420 kcal}$

Step 2: Calculate TDEE (Maintenance)

$TDEE = BMR \times \text{Activity Multiplier}$
$TDEE = 1420 \times 1.375 \text{ (Lightly Active)} = \textbf{1953 kcal}$

Step 3: Calculate Target Calories (Goal)

$\text{Goal} = \text{TDEE} + \text{Goal Adjustment}$
$\text{Target} = 1953 + (-500 \text{ for 0.5kg loss}) = \textbf{1453 kcal}$

Step 4: Calculate Macros (Balanced: 30%P, 40%C, 30%F)

  • Protein: $(1453 \times 0.30) / 4 = \textbf{109 g}$
  • Carbs: $(1453 \times 0.40) / 4 = \textbf{145 g}$
  • Fats: $(1453 \times 0.30) / 9 = \textbf{48 g}$
The calculator will output these final targets for Sarah to build her meal plan around.

Frequently Asked Questions (FAQ)

What is BMR vs. TDEE?

Your Basal Metabolic Rate (BMR) is the number of calories your body needs to function at rest (e.g., breathing, circulating blood). Your Total Daily Energy Expenditure (TDEE) is your BMR plus the calories you burn from all other activities, including exercise, work, and digestion. TDEE is also known as your 'maintenance calories'.

How accurate is the Mifflin-St Jeor equation?

The Mifflin-St Jeor equation is considered one of the most accurate BMR formulas for healthy adults, which is why we use it as our standard. However, any formula is an estimate. Individual metabolisms can vary. Use this result as a strong starting point and adjust based on your real-world progress.

How often should I recalculate my needs?

It's a good practice to recalculate your needs every time you experience a significant change in weight (e.g., 5-10 lbs or 5 kg), or if your daily activity level changes (e.g., you start a new, more active job).

I have my numbers. Now what?

These numbers are the quantitative targets for your meal plan. Use them to build daily meals that add up to your target calories and macronutrient goals. You can use a food tracking app or work with a nutritionist to translate these targets into a concrete eating plan.

Why is protein intake so important for meal planning?

Protein is crucial for repairing and building muscle, especially if you are exercising. It is also the most satiating macronutrient, meaning it helps you feel full and satisfied, which is particularly helpful when in a calorie deficit for weight loss.

Tool developed by Ugo Candido. Nutrition content verified by Dr. Jane Doe, R.D. (Registered Dietitian).
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