How it works
Sustainable weight loss is governed by the first law of thermodynamics—energy balance. When you consume fewer calories than your body expends for basal metabolism and physical activity (your TDEE), your body bridges that energy gap by oxidizing stored adipose tissue. This calculator uses the clinically validated Mifflin-St Jeor equation to compute your BMR and TDEE, applies your chosen daily deficit with a built-in safety floor, and projects the exact calendar date you will reach your goal weight.
Comparison of Daily Calorie Deficit Levels & Fat Loss Speed
Because each 1.0 kg (2.2 lbs) of human body fat stores roughly 7,700 kcal, your chosen daily deficit directly determines your weekly and monthly rate of weight loss:
| Daily Calorie Deficit | Weekly Weight Loss | Monthly Weight Loss | Best Suited For |
|---|---|---|---|
| Mild Deficit (-300 kcal/day) | 0.27 kg / week (0.6 lb) | 1.17 kg / month | Leaner individuals, athletes, or final 3–5 kg cut |
| Standard Deficit (-500 kcal/day) | 0.45 kg / week (1.0 lb) | 1.95 kg / month | Gold-standard sustainable fat loss with minimal hunger |
| Moderate-High (-750 kcal/day) | 0.68 kg / week (1.5 lbs) | 2.92 kg / month | Individuals with 15+ kg to lose and high protein intake |
| Maximum Deficit (-1,000 kcal/day) | 0.91 kg / week (2.0 lbs) | 3.90 kg / month | Higher starting weights (subject to 1,200 kcal floor) |
How Your Daily Target & Goal Date Are Calculated
- Basal Metabolic Rate (BMR): Computed via the Mifflin-St Jeor formula:
10 × weight(kg) + 6.25 × height(cm) − 5 × age(y) + 5(for men) or− 161(for women). - Total Daily Energy Expenditure (TDEE): Multiplies BMR by your physical activity factor (from 1.2 for sedentary to 1.9 for very heavy training).
- Daily Target Calories: Subtracts your selected deficit from TDEE while enforcing a minimum nutritional safety floor of 1,200 kcal/day.
- Days to Goal Weight:
Total Days = [ (Current Weight − Goal Weight) × 7,700 ] ÷ Actual Daily Deficit.
A 30-year-old male, 175 cm tall, currently weighing 85 kg wants to reach 75 kg (lose 10 kg) with light exercise and a 500 kcal/day deficit:
- Basal Metabolic Rate (BMR): 1,799 kcal/day.
- Maintenance Calories (TDEE): 1,799 × 1.375 = 2,473 kcal/day.
- Target Daily Calorie Intake: 2,473 − 500 = 1,973 kcal/day.
- Total Energy to Burn for 10 kg Fat Loss: 10 × 7,700 = 77,000 kcal.
- Time Required to Reach 75 kg: 77,000 ÷ 500 = 154 days (~22 weeks at 0.45 kg/week).
Split your daily target calories into optimal protein, carbs, and fats with the /en/macro-calculator, verify your maintenance energy expenditure in the /en/tdee-calculator, check your weight category with the /en/bmi-calculator, and track body composition using the /en/body-fat-calculator.