Bodybuilding Calculations Explained (With Formulas & Logic)

 🏋️‍♂️ Bodybuilding Calculations Explained (With Formulas & Logic)

 

 

 

Building your dream physique is not just about lifting heavy weights — it’s about understanding your body scientifically.

To achieve fat loss, muscle gain, or overall fitness, you need to calculate your body’s needs accurately.

Let’s explore the most important bodybuilding calculations with formulas and simple logic.

🔹 1. BMI (Body Mass Index)

Purpose: To check if your body weight is within a healthy range.

Formula:

BMI = \frac{Weight (kg)}{[Height (m)]^2}

Example:

If you weigh 70 kg and your height is 1.75 m:

BMI = 70 / (1.75 × 1.75) = 22.86

Logic:

BMI helps identify whether you are underweight, normal, overweight, or obese.

However, bodybuilders may have a higher BMI due to muscle mass, not fat — so it’s not always a perfect indicator.

🔹 2. BMR (Basal Metabolic Rate)

Purpose: Shows how many calories your body burns at rest (for basic survival like breathing, digestion, etc.).

Formula (Mifflin–St Jeor Equation):

For Men:

BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5

BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age - 161

Example:

A 25-year-old male, 70kg, 175cm tall:

BMR = 10×70 + 6.25×175 - 5×25 + 5 = 1673.75 \text{ kcal/day}

Logic:

BMR tells you the minimum calories your body needs to stay alive.

Knowing this helps you decide how much to eat for fat loss or muscle gain.

🔹 3. TDEE (Total Daily Energy Expenditure)

Purpose: Shows your total calorie burn per day (including workouts & activity).

Formula:

TDEE = BMR × Activity\ Level

Activity Multipliers:

Sedentary (little/no exercise): 1.2

Lightly active (1–3 days/week): 1.375

Moderately active (3–5 days/week): 1.55

Very active (6–7 days/week): 1.725

Example:

If your BMR = 1674 and you work out 4 times/week (moderately active):

TDEE = 1674 × 1.55 = 2595 \text{ kcal/day}

Logic:

TDEE shows your maintenance calories.

👉 Eat less than TDEE for fat loss,

👉 Eat more than TDEE for muscle gain.

🔹 4. Calorie Deficit (for Fat Loss)

Purpose: To plan how many calories to reduce for losing fat safely.

Formula:

Calorie\ Deficit = TDEE - 500

Example:

If TDEE = 2600 kcal/day →

2600 - 500 = 2100 \text{ kcal/day (for fat loss)}

Logic:

A 500-calorie deficit per day helps you lose around 0.5 kg of fat per week — healthy and sustainable progress.

🔹 5. Calorie Surplus (for Muscle Gain)

Purpose: To plan how many extra calories to eat for gaining muscle.

Formula:

Calorie\ Surplus = TDEE + 300

Example:

If TDEE = 2600 →

2600 + 300 = 2900 \text{ kcal/day (for muscle gain)}

Logic:

A moderate surplus ensures you gain lean muscle, not fat.

Combine this with proper protein and strength training.

🔹 6. Protein Intake

Purpose: Supports muscle growth and recovery.

Formula (general rule):

Protein = 1.6–2.2g × body\ weight(kg)

Example:

If you weigh 70kg:

70 × 2 = 140g\ of\ protein/day

Logic:

Protein repairs and builds muscle tissues after training.

Higher protein intake = better muscle recovery and growth.

🔹 7. One Rep Max (1RM)

Purpose: To find your maximum lifting strength for one repetition.

Formula (Epley’s Formula):

1RM = Weight × (1 + \frac{Reps}{30})

Example:

If you lift 60 kg for 10 reps:

1RM = 60 × (1 + 10/30) = 80 kg

Logic:

Helps you plan workout intensity safely and progressively overload for muscle growth.

🔹 8. Water Intake

Purpose: Keeps you hydrated for better strength and metabolism.

Formula:

Water\ (liters) = Weight(kg) × 0.033

Example:

If weight = 70 kg →

70 × 0.033 = 2.31L/day

Logic:

Proper hydration improves strength, recovery, and digestion.

🧠 Final Thoughts

Bodybuilding is a mix of math + discipline + patience.

Once you understand these basic calculations — you can create your own customized diet and workout plan with accurate results.

💡 Tip: Always track your progress every 2–4 weeks and adjust calories or training intensity accordingly.