Estimate how many weeks it could take to reach your goal weight at a steady daily calorie deficit.
This calculator estimates how long it will take to reach a goal weight based on a steady daily calorie deficit, using the widely cited energy-equivalent of body fat.
Estimated Days = (Weight to Lose × Calories per Unit) ÷ Daily Calorie Deficit. About 3,500 kcal roughly correspond to one pound of body fat, or about 7,700 kcal per kilogram.
Losing 20 lb with a 500 kcal/day deficit needs 70,000 kcal total (20 × 3,500), which takes about 140 days, or 20 weeks.
Very large deficits are hard to sustain and can slow metabolism. A deficit of 500–750 kcal/day is generally considered a sustainable pace for most adults.
Total goal divided by an expected rate of loss based on your calorie deficit.
This rate is generally sustainable and more likely to preserve muscle mass long-term.
No — real-world loss often fluctuates week to week even with a consistent deficit.