How the math works#
A kilogram of body fat stores roughly 7,700 kcal (about 3,500 kcal per pound). To lose 0.5 kg per week you need a weekly deficit of about 3,850 kcal — 550 kcal per day below your maintenance. This calculator estimates maintenance with the Mifflin-St Jeor equation and your activity level, subtracts the deficit for your chosen rate, and projects the timeline to your goal.
Choosing a rate#
- 0.25 kg/week — slow and almost effortless; best when you are already lean.
- 0.5 kg/week — the sweet spot for most people: meaningful progress, preserved muscle, livable hunger.
- 0.75–1 kg/week — aggressive; workable for higher starting body fat, but keep protein high and expect the last weeks to be hard.
Why real progress is bumpier than the projection#
Two things bend the straight line. First, your TDEE drops as you get lighter — recalculate every 4–5 kg lost. Second, water masks fat loss: sodium, carbs, stress, and training all move the scale day to day. Weigh in a few times a week and judge the two-week trend, not this morning's number.
Keep lifting through the deficit and hold protein at cutting levels (1.8–2.4 g/kg) — that is what tells your body to burn fat instead of muscle.