How long does it take to lose 10 kg (22 lb)?
Ten kilograms — about 22 lb — of body fat is roughly 77,000 kcal. Divide that by your daily deficit and you have an answer — on paper.
The table
| Daily deficit | Days | Weeks | Roughly |
|---|---|---|---|
| 250 kcal | 308 | 44 | 10 months |
| 500 kcal | 154 | 22 | 5 months |
| 750 kcal | 103 | 15 | 3.5 months |
| 1,000 kcal | 77 | 11 | 2.5 months |
That is the arithmetic. The honest answer is that most people land somewhere slower than the row they picked, for reasons worth knowing in advance.
What a safe rate looks like
The usual guidance is 0.5 to 1 kg (1–2 lb) per week, which corresponds to a deficit of roughly 550 to 1,100 kcal per day. For most people that puts 10 kg somewhere between three and five months.
Going harder is possible and mostly counterproductive. Very aggressive deficits cost more lean tissue, make training feel awful, and — the part that actually decides outcomes — are much harder to stay on. A 500 kcal deficit you hold for five months beats a 1,000 kcal deficit you abandon in three weeks.
Why reality runs slower
The first fortnight flatters you. Glycogen and its associated water go early, so the scale drops faster than fat loss justifies. This reverses later: around week three the scale appears to stop while fat loss continues unchanged. Nothing has gone wrong.
Your deficit shrinks as you do. A lighter body burns less at rest. Lose 5 kg (11 lb) and your resting burn may fall by 50–70 kcal per day without you changing anything — so a deficit calculated at the start quietly erodes.
You move less without noticing. Non-exercise activity — fidgeting, walking, standing — tends to drop in a deficit. It is unconscious and can account for a few hundred calories a day.
Intake gets under-reported. Not dishonesty; just oil in the pan, a handful of something, portions estimated generously. Reliably studied, reliably large.
Reading your own numbers instead
Because the inputs drift, a projection made on day one is worth very little by month two. What is worth tracking is your actual average deficit so far, and recomputing the finish date from it.
That is how Caldown’s projection works: it uses your real rolling average rather than the number you typed at setup, so the end date moves as your behaviour does — earlier on a good fortnight, later after a bad one. It is a measurement, not a promise.
A sensible way to set the goal
- Pick a deficit you can hold on an ordinary week, not an ideal one.
- Expect the first two weeks to over-report and week three to under-report.
- Judge progress on a four-week trend, never on a single morning.
- Re-check your maintenance burn every 5 kg (11 lb) or so.
If you want the arithmetic behind the 77,000, it is in how many calories are in 1 kg of fat, and the calorie deficit guide covers the rest of the method.
General information, not medical advice. Talk to a doctor or registered dietitian before a significant change to how you eat, particularly if you have any health condition.