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Fat Loss Calculator

Calculate your estimated fat loss timeline, calorie requirements, and create a personalized plan to reach your weight loss goals safely and effectively.

Your current weight in kilograms (kg)
Your target weight in kilograms (kg)
Your height in centimeters (cm)
Your age in years
Recommended: 0.5-0.8 kg per week for sustainable fat loss
Check to include exercise recommendations in your plan

How to Use This Calculator

  1. Enter your current weight in kilograms (kg)
  2. Input your goal weight (target weight)
  3. Provide your height in centimeters (cm) and age in years
  4. Select your gender and activity level
  5. Adjust the weight loss rate slider to your preference
  6. Click Calculate to see your personalized fat loss plan

Formula Used

BMR = 10 × Weight(kg) + 6.25 × Height(cm) - 5 × Age(y) + Gender Factor
TDEE = BMR × Activity Level
Calorie Deficit = TDEE - (TDEE × Deficit Percentage)

Where:

  • BMR = Basal Metabolic Rate (calories burned at rest)
  • TDEE = Total Daily Energy Expenditure (total calories burned daily)
  • Gender Factor = +5 for males, -161 for females
  • Activity Level = Multiplier based on physical activity (1.2-1.9)
  • Deficit Percentage = Calorie reduction for weight loss (15-30%)

Example Calculation

Real-World Scenario:

A 35-year-old female who is 165cm tall, weighs 75kg, wants to lose 10kg, and is moderately active.

Given:

  • Weight = 75 kg
  • Height = 165 cm
  • Age = 35 years
  • Gender = Female
  • Activity Level = Moderately active (1.55)
  • Weight Loss Rate = 0.5 kg/week

Calculation:

BMR = 10 × 75 + 6.25 × 165 - 5 × 35 - 161 = 750 + 1031.25 - 175 - 161 = 1,445.25 calories

TDEE = 1,445.25 × 1.55 = 2,240 calories

Calorie Deficit = 2,240 - (2,240 × 0.25) = 2,240 - 560 = 1,680 calories

Time to Goal = 10 kg ÷ 0.5 kg/week = 20 weeks

Result: A 20-week fat loss plan with a daily target of 1,680 calories, creating a 560-calorie daily deficit for sustainable weight loss.

Why This Calculation Matters

Practical Applications

  • Creating a personalized calorie target for weight loss
  • Setting realistic timelines for reaching weight goals
  • Preventing excessive calorie restriction and muscle loss
  • Understanding the relationship between calories and weight loss
  • Establishing sustainable eating habits for long-term success

Key Benefits

  • Helps avoid crash dieting and yo-yo weight cycling
  • Promotes fat loss while preserving muscle mass
  • Provides a clear roadmap to weight loss goals
  • Reduces risk of nutrient deficiencies and metabolic damage
  • Improves long-term weight maintenance success rates

Common Mistakes & Tips

Many people set unrealistic weight loss goals of 1-2 kg per week, which is often unsustainable and leads to muscle loss. A healthy rate of fat loss is typically 0.5-0.8 kg per week. Faster weight loss usually includes water weight and muscle tissue, not just fat. Focus on sustainable changes that you can maintain long-term rather than quick fixes.

Severely restricting calories below your BMR can slow your metabolism and lead to muscle loss. Women should generally not eat below 1,200 calories per day, and men not below 1,500 calories. Instead of extreme restriction, focus on creating a moderate deficit of 15-30% below your TDEE. This approach preserves muscle mass and metabolic rate while still promoting steady fat loss.

During weight loss, consuming adequate protein (1.6-2.2g per kg of body weight) and performing resistance training are crucial for preserving muscle mass. Without these, up to 25% of weight loss can come from muscle rather than fat. Muscle preservation helps maintain metabolic rate and improves body composition. Include protein sources with each meal and perform strength training 2-3 times per week.

Frequently Asked Questions

This calculator provides estimates based on established formulas like Mifflin-St Jeor for BMR and standard activity multipliers. While these formulas are scientifically validated, individual variations in metabolism, genetics, and body composition can affect actual calorie needs. The calculator is most accurate when you provide complete and honest information about your activity level. Consider the results as a starting point that may need adjustment based on your actual progress.

Weight loss plateaus are common and can occur for several reasons. As you lose weight, your BMR decreases, meaning you burn fewer calories at rest. Additionally, your body may adapt to lower calorie intake by reducing energy expenditure. To break through a plateau, consider recalculating your needs with your new weight, increasing physical activity, or trying a brief period of eating at maintenance calories before resuming your deficit. Also ensure you're accurately tracking your food intake.

Yes, it's important to adjust your calorie intake as you lose weight. For every 5kg (11lbs) of weight loss, your BMR decreases by approximately 30-50 calories per day. This means the calorie target that initially created a deficit will eventually become your new maintenance level. To continue losing weight, recalculate your needs every 5-10kg of weight loss or every 4-6 weeks, whichever comes first. This ensures you maintain an appropriate deficit throughout your weight loss journey.

Spot reduction, or losing fat from specific areas of the body, is a common myth. Unfortunately, you can't choose where your body loses fat. Genetics largely determine where you store and lose fat first. However, you can improve the appearance of specific areas through a combination of overall fat loss and muscle building. For example, building muscle in your abdominal area through resistance training can improve the appearance of your midsection as you lose body fat throughout your entire body.

References & Disclaimer

Medical Disclaimer

This calculator provides estimates only and should not be considered medical advice. Individual nutritional needs vary based on numerous factors including genetics, health status, and activity level. Consult with a healthcare professional or registered dietitian before making significant changes to your diet or exercise routine, especially if you have underlying health conditions such as diabetes, heart disease, or metabolic disorders.

References

Accuracy Notice

The calculations provided by this tool are estimates based on established nutritional science. Individual results may vary based on factors not accounted for in the calculator, such as metabolic health, hormonal status, genetic factors, and body composition. This calculator should be used for informational purposes only and not as a substitute for professional medical or nutritional guidance.

About the Author

Kumaravel Madhavan

Web developer and data researcher creating accurate, easy-to-use calculators across health, finance, education, and construction and more. Works with subject-matter experts to ensure formulas meet trusted standards like WHO, NIH, and ISO.

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health nutrition-diet-planning fat loss medical body weight