Scientifically calculate your calorie deficit, TDEE, and weight loss timeline.
1. Personal Details
Please enter a valid age (18-100).
Used to calculate your Basal Metabolic Rate (BMR).
2. Goals & Activity
Goal weight must be less than current weight.
Sedentary (Office job, little exercise)
Lightly Active (Exercise 1-3 days/week)
Moderately Active (Exercise 3-5 days/week)
Very Active (Exercise 6-7 days/week)
Extra Active (Physical job + exercise)
Be honest! Overestimating activity is a common mistake.
Slow & Steady (0.25 kg / 0.5 lb per week)
Recommended (0.5 kg / 1 lb per week)
Aggressive (0.75 kg / 1.5 lb per week)
Very Aggressive (1.0 kg / 2 lb per week)
Faster isn't always better. Sustainable loss is key.
A diet weight loss calculator is a specialized financial and biological planning tool designed to help individuals determine the precise mathematical requirements to lose body mass. Unlike generic advice, this calculator uses your specific biometric data to compute your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE).
By establishing a controlled "caloric deficit"—the state where you consume fewer calories than your body burns—you can predict weight loss with reasonable accuracy. This tool is essential for anyone looking to manage their weight systematically, whether for health reasons, athletic performance, or personal aesthetics.
Common misconceptions include the idea that all calories are equal or that weight loss is purely linear. While the math provides a solid framework, biological adaptations and water retention can cause fluctuations. This calculator provides a "perfect world" projection to guide your daily decisions.
Diet Weight Loss Calculator Formula and Explanation
The core of any accurate diet weight loss calculator is the estimation of energy expenditure. We utilize the Mifflin-St Jeor Equation, which is widely considered the most accurate standard for estimating BMR in clinical settings.
Step 1: Calculate BMR
Your Basal Metabolic Rate is the energy your body needs just to exist at rest.
Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
Step 2: Calculate TDEE
We multiply BMR by an Activity Factor to find your Total Daily Energy Expenditure.
Variable
Meaning
Multiplier
Sedentary
Desk job, little to no exercise
1.2
Lightly Active
Light exercise 1-3 days/week
1.375
Moderately Active
Moderate exercise 3-5 days/week
1.55
Very Active
Hard exercise 6-7 days/week
1.725
Step 3: The Deficit
To lose weight, we subtract calories from the TDEE. The standard scientific consensus is that approximately 3,500 calories equals 1 pound of fat (or ~7,700 calories for 1 kg).
Profile: John, 35 years old, 180cm, 95kg. Sedentary job.
Goal: Reach 85kg.
BMR: ~1,950 kcal
TDEE (Sedentary): 1,950 × 1.2 = 2,340 kcal
Strategy: Lose 0.5kg per week (500 kcal deficit).
Daily Target: 2,340 – 500 = 1,840 kcal.
Timeline: To lose 10kg at 0.5kg/week takes 20 weeks.
Example 2: The Active Professional
Profile: Sarah, 28 years old, 165cm, 70kg. Exercises 4 days a week.
Goal: Reach 65kg.
BMR: ~1,450 kcal
TDEE (Moderate): 1,450 × 1.55 = 2,247 kcal
Strategy: Lose 0.5kg per week.
Daily Target: 2,247 – 500 = 1,747 kcal.
Timeline: To lose 5kg takes 10 weeks.
How to Use This Diet Weight Loss Calculator
Enter Biometrics: Input your gender, age, height, and current weight accurately.
Select Activity Level: Be honest. Most people overestimate this. If you have a desk job but go to the gym for an hour, you are likely "Lightly Active" or "Moderately Active," not "Very Active."
Set Your Goal: Enter your target weight.
Choose Pace: Select how fast you want to lose weight. We recommend 0.5kg (1lb) per week for sustainable results.
Review Results: The calculator will show your daily calorie budget. Stick to this number consistently.
Key Factors That Affect Diet Weight Loss Calculator Results
While the math is precise, human biology is complex. Here are six factors that influence your actual results:
Metabolic Adaptation: As you lose weight, your body becomes smaller and more efficient, lowering your BMR. You may need to adjust calories down further as you progress.
Non-Exercise Activity Thermogenesis (NEAT): This is the energy burned by fidgeting, walking, and standing. Dieting often subconsciously reduces NEAT, slowing weight loss.
Macronutrient Composition: Protein has a higher "thermic effect" than fats or carbs, meaning your body burns more calories digesting it. High-protein diets often yield better results.
Water Retention: High salt intake, stress (cortisol), and hormonal cycles can cause water retention, masking fat loss on the scale for days or weeks.
Sleep Quality: Poor sleep disrupts hunger hormones (ghrelin and leptin), often leading to overeating and reduced metabolic rate.
Accuracy of Tracking: Most people underestimate their food intake by 20-30%. Using a food scale is crucial for matching the calculator's output.
Frequently Asked Questions (FAQ)
Is it safe to lose weight faster than the calculator recommends?
Generally, no. Losing more than 1% of your body weight per week can lead to muscle loss, gallstones, and nutritional deficiencies. Rapid weight loss is also harder to maintain long-term.
Why am I not losing weight even though I stick to the calories?
You may be underestimating your intake (hidden calories in oils/sauces) or overestimating your activity level. Also, water retention can mask fat loss temporarily.
Does this calculator account for muscle gain?
No. This calculator focuses on body weight. If you are lifting heavy weights and eating high protein, you might lose fat but gain muscle, keeping your weight stable while your body composition improves.
What is the minimum calorie intake I should have?
Health organizations generally recommend not dropping below 1,200 kcal for women and 1,500 kcal for men without medical supervision to ensure adequate nutrient intake.
Should I eat back my exercise calories?
Be cautious. Fitness trackers often overestimate calories burned. It is usually safer to stick to your TDEE-based deficit rather than adding back every calorie burned during a workout.
How often should I recalculate?
You should recalculate every time you lose 5-10 lbs (2-5 kg), as your BMR will decrease with your new lower body weight.
Can I target fat loss in specific areas (belly fat)?
No. "Spot reduction" is a myth. A caloric deficit causes fat loss across the entire body, determined by genetics.
What is a "refeed" day?
A refeed day involves eating at maintenance calories (usually higher carbs) to boost leptin levels and mental well-being. It is not a "cheat day" where you binge eat.
Related Tools and Internal Resources
BMI Calculator – Check if your weight is within a healthy range.
Macro Calculator – Detailed breakdown of protein, fats, and carbs.
BMR Calculator – Calculate your Basal Metabolic Rate specifically.