TDEE Calculator

def mifflin_bmr(weight_kg, height_cm, age, sex):
    """
    Mifflin-St Jeor BMR formula (1990).

    Parameters:
        weight_kg  - body weight in kilograms
        height_cm  - height in centimetres
        age        - age in years
        sex        - 'male' or 'female'

    Returns BMR in kcal/day.
    """
    bmr = 10 * weight_kg + 6.25 * height_cm - 5 * age
    bmr += 5 if sex.lower() == 'male' else -161
    return bmr

def tdee(weight_kg, height_cm, age, sex, activity_level='sedentary'):
    """
    Calculate Total Daily Energy Expenditure (TDEE).

    Activity multipliers (Mifflin-St Jeor):
        sedentary        1.2   (desk job, little/no exercise)
        light            1.375 (1-3 days/week exercise)
        moderate         1.55  (3-5 days/week exercise)
        active           1.725 (6-7 days/week hard exercise)
        very_active      1.9   (physical job + hard exercise)
    """
    multipliers = {
        'sedentary':   1.2,
        'light':       1.375,
        'moderate':    1.55,
        'active':      1.725,
        'very_active': 1.9,
    }
    bmr = mifflin_bmr(weight_kg, height_cm, age, sex)
    factor = multipliers.get(activity_level, 1.2)
    return bmr * factor

# Example: 30-year-old male, 80 kg, 180 cm, moderately active
bmr  = mifflin_bmr(80, 180, 30, 'male')
tdee_val = tdee(80, 180, 30, 'male', 'moderate')
print(f"BMR:  {bmr:.0f} kcal/day")
print(f"TDEE: {tdee_val:.0f} kcal/day")
print(f"Weight loss target (-500 kcal): {tdee_val - 500:.0f} kcal/day")
print(f"Muscle gain target (+250 kcal): {tdee_val + 250:.0f} kcal/day")