What is the Weight Loss Timeline Calculator?
This calculator estimates how long it will take to reach a target body weight given your current weight and the daily calorie deficit you can sustain. It uses the widely cited rule that roughly 7,700 kilocalories equal one kilogram of body fat (about 3,500 kcal per pound). It is a planning tool, not medical advice.
How to use it
Enter your current weight and your goal weight in kilograms, then enter your average daily calorie deficit — the gap between calories burned and calories eaten. The calculator returns the number of days to reach your goal, plus the equivalent in weeks and months and your expected average weekly loss.
The formula explained
First the calculator finds the weight you need to lose: current − goal. Each kilogram of fat stores about 7,700 kcal, so the total energy deficit required is that weight multiplied by 7,700. Dividing by your daily deficit gives the number of days: $$\text{Days} = \frac{\left(\text{Current (kg)} - \text{Goal (kg)}\right) \times 7700}{\text{Deficit (kcal/day)}}$$
Worked example
Suppose you weigh 90 kg and want to reach 75 kg with a 500 kcal/day deficit. You need to lose 15 kg, which is $$15 \times 7700 = 115{,}500 \text{ kcal}.$$ Dividing by 500 gives 231 days — about 33 weeks or 7.6 months, averaging roughly 0.45 kg lost per week.
FAQ
Why 7700 kcal per kg? It is the approximate energy stored in a kilogram of adipose tissue. Real results vary because of water, muscle and metabolic adaptation.
Will my deficit stay constant? Not exactly — as you lose weight your maintenance calories fall, so deficits often shrink and progress slows. Treat the estimate as a best-case linear projection.
Is a 500 kcal deficit safe? A 250–500 kcal/day deficit (about 0.25–0.5 kg/week) is commonly considered sustainable, but consult a healthcare professional for personal guidance.
