Most people start a diet with a number they pulled off a generic chart. That's why most diets fail in week 1.

TDEE (Total Daily Energy Expenditure) is the only target worth using. It accounts for your size, sex, age, and activity. The formula:

    TDEE = BMR x activity multiplier

BMR (Basal Metabolic Rate) uses the Mifflin-St Jeor formula:

    Men:   10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5
    Women: 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161

Activity multipliers:

    Sedentary (desk job, no exercise):           1.2
    Lightly active (light exercise 1-3 d/wk):    1.375
    Moderately active (moderate 3-5 d/wk):       1.55
    Very active (hard 6-7 d/wk):                 1.725
    Extremely active (twice daily, hard labor):  1.9

Once you have TDEE:

- Fat loss: TDEE minus 300-500 cal/day → ~0.3-0.5 kg/wk
- Muscle gain: TDEE plus 200-400 cal/day → ~0.2-0.4 kg/wk
- Maintenance: TDEE exactly

Track for 2 weeks. If body weight isn't moving in the direction you want, adjust by 100-200 cal and reassess in another 2 weeks. Don't change the target every few days based on water-weight noise.

Free calculator + the full math: https://virtusapp.ai/blog/calorie-calculator/

How to actually calculate your daily calories (TDEE method, with the math)