How it is calculated
- Weeks = (current weight − goal weight) ÷ weekly rate, rounded up
- Target date = start date + (weeks × 7) days
- Daily calorie deficit = weekly rate × 7,700 ÷ 7
If you enter your TDEE and your TDEE minus the daily deficit is below 1,200 kcal (women) or 1,500 kcal (men), the calculator shows a warning.
The 7,700 kcal per kg of body fat figure is a common approximation. If the goal weight is not lower than the current weight, the calculator shows an error. Estimate only, not medical advice.
Worked example
Going from 80 kg to 70 kg at 0.5 kg per week, starting 1 January 2026:
- (80 − 70) ÷ 0.5 = 20 weeks
- 1 January 2026 + 140 days = 21 May 2026
- Daily deficit = 0.5 × 7,700 ÷ 7 = 550 kcal
- If you are a woman and your TDEE is 1,700 kcal: 1,700 − 550 = 1,150 kcal, below 1,200, so the warning appears
Why your number may differ
The 7,700 kcal per kg rule is an approximation; actual loss usually slows over time as your body adapts. Many guidelines, including the Malaysian Clinical Practice Guidelines on Management of Obesity (2023), suggest about 1,200 to 1,500 kcal per day for women and 1,500 to 1,800 kcal per day for men for an initial loss of 0.5 to 1 kg per week. Very low calorie diets (under 800 kcal per day) should only be followed under medical supervision. See a doctor if you have a medical condition. Estimate only, not medical advice.