Understanding Your Calorie Needs
Your daily calorie requirement depends on your basal metabolic rate (BMR) — the energy your body needs at complete rest — multiplied by an activity factor to give your Total Daily Energy Expenditure (TDEE).
BMR
Basal Metabolic Rate — calories burned at rest just to keep you alive. Your floor.
TDEE
Total Daily Energy Expenditure — BMR × activity factor. Your maintenance calorie level.
Deficit
Eating below TDEE creates a calorie deficit. A 500 kcal/day deficit = ~0.45 kg (1 lb) lost per week.
Surplus
Eating above TDEE creates a surplus. Combined with resistance training, this builds muscle mass.
Which Formula Should I Use?
- Mifflin-St Jeor — Most accurate for the general population. Recommended for most users.
- Harris-Benedict (revised) — Classic formula, slightly less accurate but widely used.
- Katch-McArdle — Most accurate if you know your body fat percentage. Best for athletes.
Limitations
These formulas provide estimates. Actual calorie needs vary due to genetics, hormones, gut microbiome, medication, and medical conditions. Tracking actual intake and adjusting based on real results over 2–4 weeks is more reliable than calculator estimates alone.