What Is the Weight Loss Timeline Calculator?
This calculator estimates how long it will take to reach a target weight given a consistent daily calorie deficit. It is based on the widely used approximation that roughly 7,700 kcal equals one kilogram of body fat. By dividing the total energy gap between your current and goal weight by your daily (and weekly) calorie shortfall, it returns the time in weeks, days, and months.
How to Use It
Enter your current weight and your goal weight in kilograms, then enter the daily calorie deficit you plan to maintain (the difference between calories eaten and calories burned). A deficit of 500 kcal/day is a common, sustainable target. The calculator then shows your estimated timeline plus how much weight you should lose each week.
The Formula Explained
$$\text{Weeks} = \frac{\left(\text{Current (kg)} - \text{Goal (kg)}\right) \times 7700}{\text{Deficit (kcal/day)} \times 7}$$ The numerator is the total calories your body must burn from fat stores; the denominator is the calories you cut each week. Weekly weight loss is simply the weekly deficit divided by 7700.
Worked Example
Suppose you weigh 85 kg, want to reach 75 kg, and maintain a 500 kcal/day deficit. You need to lose 10 kg, which is \(10 \times 7700 = 77{,}000\) kcal. Your weekly deficit is \(500 \times 7 = 3{,}500\) kcal, so $$\text{Weeks} = \frac{77{,}000}{3{,}500} = 22 \text{ weeks}$$ (about 5.1 months), losing roughly 0.45 kg per week.
FAQ
Is 7,700 kcal per kg accurate? It is a useful estimate. Real-world loss varies with metabolism, water weight, and adaptive changes, so treat the timeline as a guide.
What is a safe deficit? Many guidelines suggest 500–750 kcal/day for steady loss of about 0.5–0.7 kg per week. Very large deficits can be hard to sustain.
Will my rate slow over time? Often yes — as you lose weight, your maintenance calories drop, so you may need to adjust your deficit to keep progressing.
