Muscle Gain Calculator Formula

Understand the math behind the muscle gain calculator. Each variable explained with a worked example.

Use the Muscle Gain Calculator

Formulas Used

Bulking Calories/day

bulking_calories = tdee + surplus

Protein Target (1g/lb)

protein_grams = weight_lbs * 1.0

Estimated Weekly Gain

weight_gain_weekly = surplus * 7 / 3500

Maintenance TDEE

tdee_display = tdee

Variables

VariableDescriptionDefault
weight_lbsBody Weight(lbs)170
height_inches_totalHeight (total inches)(inches)70
ageAge(years)25
surplusDaily Caloric Surplus(cal)300
weight_kgDerived value= weight_lbs * 0.453592calculated
height_cmDerived value= height_inches_total * 2.54calculated
bmrDerived value= 10 * weight_kg + 6.25 * height_cm - 5 * age + 5calculated
tdeeDerived value= bmr * 1.55calculated

How It Works

Muscle Gain Nutrition

To build muscle, you need a caloric surplus above your TDEE plus adequate protein.

Guidelines

  • Caloric surplus: 200-500 cal/day above TDEE
  • Protein: 0.8-1.0 g per lb body weight
  • Expected gain: 0.5-1 lb per week (surplus of 250-500 cal/day)

    • BMR is calculated with the Mifflin-St Jeor formula. TDEE assumes moderate activity (factor 1.55).

    Worked Example

    A 25-year-old, 170 lbs, 70 inches tall, moderate surplus (+300 cal).

    weight_lbs = 170height_inches_total = 70age = 25surplus = 300
    1. 01BMR = 10(77.1) + 6.25(177.8) - 5(25) + 5 = 1,762
    2. 02TDEE = 1,762 x 1.55 = 2,731
    3. 03Bulking calories = 2,731 + 300 = 3,031 cal/day
    4. 04Protein = 170 x 1.0 = 170 g/day
    5. 05Weekly gain = 300 x 7 / 3500 = 0.60 lbs

    Ready to run the numbers?

    Open Muscle Gain Calculator