Weight Loss Calculator
Calculate how long it will take to reach your goal weight. Get a personalized timeline, daily calorie target, and projected weight loss chart. Based on the Mifflin-St Jeor equation. 100% private — nothing leaves your browser.
How the Weight Loss Calculator Works
This calculator uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR), then multiplies it by your activity level to find your Total Daily Energy Expenditure (TDEE). Based on your chosen weight loss pace, it calculates the daily calorie deficit needed and projects how long it will take to reach your goal weight. The calculator enforces safe calorie floors — 1,200 for women and 1,500 for men — and adjusts the timeline if your selected pace exceeds safe limits.
Mifflin-St Jeor Equation
Male BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5
Female BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161
TDEE = BMR x Activity Multiplier
Daily Deficit = Pace (kg/week) x 7,700 / 7
Safe Weight Loss Rates Explained
Health professionals recommend losing 0.5 to 1 kg per week for sustainable results. Losing weight too fast can lead to muscle loss, nutritional deficiencies, gallstones, and metabolic slowdown. A slow pace of 0.25 kg per week is ideal for those close to their goal or who want minimal lifestyle disruption. A moderate pace of 0.5 kg per week balances speed and sustainability. Faster rates above 0.75 kg per week require larger calorie deficits and should be monitored by a healthcare provider.
Calories and Weight Loss: The Science
One kilogram of body fat stores roughly 7,700 calories. To lose 0.5 kg per week, you need a daily deficit of about 550 calories. Your body burns calories through three channels: BMR (about 60-70% of total burn), the thermic effect of food (about 10%), and physical activity (20-30%). By understanding your TDEE, you can create a precise deficit through diet, exercise, or both — without guessing or starving yourself.
Setting Realistic Weight Loss Goals
A realistic goal considers your starting weight, body composition, age, and lifestyle. Aim to lose no more than 1% of your body weight per week. If you weigh 90 kg, that means no more than 0.9 kg per week. Set milestone goals — every 5 kg lost is worth celebrating. Remember that weight loss is not linear: water retention, hormonal shifts, and muscle gain can cause fluctuations even when you are in a deficit. Focus on the trend over weeks, not daily weigh-ins.
Tips to Stay on Track
Track your food intake consistently — studies show people who log meals lose twice as much weight. Prioritize protein (1.6-2.2 g per kg of body weight) to preserve muscle mass. Get 7-9 hours of sleep, as poor sleep increases hunger hormones. Stay hydrated — thirst is often confused with hunger. Build a calorie deficit you can maintain: a 300-calorie deficit is better than a 1,000-calorie deficit you abandon after two weeks. Finally, incorporate resistance training to maintain muscle and boost your metabolic rate during weight loss.
Frequently Asked Questions
How does the weight loss calculator work?
The calculator uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR), then multiplies by your activity level to find your TDEE. It subtracts a calorie deficit based on your chosen pace to determine your daily calorie target and projects when you will reach your goal weight.
What is a safe rate of weight loss?
Most health organizations recommend losing 0.5 to 1 kg (1 to 2 lbs) per week. Losing faster than this increases the risk of muscle loss, nutritional deficiencies, and metabolic slowdown. The calculator enforces minimum calorie floors of 1,200 for women and 1,500 for men.
Why does the calculator change my pace?
If your selected pace would require eating fewer calories than the safe floor (1,200 for women, 1,500 for men), the calculator automatically adjusts to a slower pace that keeps your daily intake at or above the floor. This protects against dangerous calorie restriction.
How accurate is this calculator?
The Mifflin-St Jeor equation is accurate to within about 10% for most healthy adults. However, individual factors like muscle mass, genetics, medications, and hormonal conditions can affect your actual metabolic rate. Use the results as a starting point and adjust based on real-world progress.
What is TDEE?
TDEE stands for Total Daily Energy Expenditure — the total calories your body burns per day including your BMR, physical activity, and the thermic effect of food. To lose weight, you need to eat fewer calories than your TDEE.
Is my data private?
Yes. All calculations run entirely in your browser. No personal health data is sent to any server. Your inputs are saved locally for convenience and can be cleared at any time.