Energy Balance
Calories measure energy from food. TDEE (Total Daily Energy Expenditure) is how much you burn per day including BMR (at rest), digestion, and activity.
Weight trend ≈ Calories in − Calories out
Over time, a sustained deficit tends to reduce weight; a surplus tends to increase it — physiology and hormones modulate this in real life.
BMR and Activity Multipliers
BMR estimates resting metabolism (often Mifflin–St Jeor or Harris–Benedict). Multiply by an activity factor:
| Level | Typical multiplier |
|---|---|
| Sedentary | ~1.2 |
| Light | ~1.375 |
| Moderate | ~1.55 |
| Very active | ~1.725 |
These are estimates — fitness trackers and lab tests can refine burn.
Macros Matter Too
Protein supports muscle during a cut; fiber aids satiety; fat and carbs both have roles. Two diets at the same calories can feel different — adherence beats perfection.
3500 kcal ≈ 1 lb of fat is a rough historical rule — individual water and lean mass changes blur the scale.
How to Use This Calorie Calculator
Enter age, sex, height, weight, and activity level. Review BMR, TDEE, and suggested targets for loss or gain. Adjust after 2–4 weeks of real data — not day-one scale noise.