Calculator Inputs
Formula Used
This calculator treats weight loss as an energy balance problem. It estimates resting energy, scales it by activity, then subtracts your planned intake.
Male BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Female BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Male BMR = 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age
Female BMR = 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age
BMR = 370 + 21.6 × lean mass(kg)
Lean mass = body weight × (1 − body fat % / 100)
TDEE = BMR × activity multiplier
Weekly loss (kg) = weekly calorie deficit ÷ 7700
Approximate weekly loss (lb) = weekly calorie deficit ÷ 3500
How to Use This Calculator
- Select metric or imperial units.
- Enter sex, age, height, weight, and activity level.
- Choose a BMR formula. Use Katch-McArdle when body fat is known.
- Select either target weekly loss or a custom daily deficit.
- Set the projection length and an optional adaptation factor.
- Enter an optional goal weight to estimate the timeline.
- Press calculate to show results above the form.
- Download the projection table as CSV or save results as PDF.
Example Data Table
| Profile | Weight | Activity | Maintenance | Deficit | Expected Weekly Loss |
|---|---|---|---|---|---|
| Office worker | 80 kg | Moderate | 2,500 kcal/day | 500 kcal/day | 0.45 kg/week |
| Endurance trainee | 70 kg | Active | 2,700 kcal/day | 350 kcal/day | 0.32 kg/week |
| Desk-based beginner | 95 kg | Light | 2,300 kcal/day | 600 kcal/day | 0.55 kg/week |
FAQs
1. What is a calorie deficit?
A calorie deficit means you eat fewer calories than your body uses. The gap between intake and energy expenditure drives the projected weight loss estimate.
2. Why does the calculator ask for activity level?
Activity level scales resting energy into maintenance energy. Higher activity usually raises total daily energy expenditure, so the same intake produces a smaller deficit.
3. Which BMR formula should I choose?
Mifflin-St Jeor is a common default. Harris-Benedict is another classic option. Katch-McArdle can be useful when body fat percentage is reasonably known.
4. Why does projected loss slow down over time?
As body weight falls, energy needs often fall too. The calculator can also apply an adaptation factor, which reduces maintenance calories during the forecast.
5. Is 7,700 kcal per kilogram exact?
No. It is a practical approximation for energy stored in body mass. Real weight change varies with water, glycogen, lean tissue, and adherence.
6. What is a safe calorie target?
There is no single safe number for everyone. The calculator shows a common minimum guidance value, but personal medical needs can differ.
7. Can I use this calculator for goal dates?
Yes. Enter an optional goal weight and the tool simulates weekly progress until the target is reached or the projection window ends.
8. Why are actual results different from estimates?
Real life includes changing hunger, activity, water balance, and tracking error. This calculator is a planning model, not a guarantee of exact loss.