Calculate your weight-loss date
Enter sex, age, height, current weight, goal weight, activity, and a weekly pace. The calculator estimates maintenance with Mifflin-St Jeor, subtracts the calorie gap for that pace, and shows a goal date.
How Weight Loss Works
Weight loss occurs when you consistently consume fewer calories than your body burns (a calorie deficit). The standard estimate is that one pound of body fat equals approximately 3,500 calories.
To lose 1 pound per week, you need a daily deficit of 500 calories (500 × 7 days = 3,500 calories). To lose 2 pounds per week, a 1,000-calorie daily deficit.
The Mifflin-St Jeor equation estimates your basal metabolic rate (BMR) — the calories burned at rest. Multiplying BMR by an activity factor gives your total daily energy expenditure (TDEE). Eating below TDEE creates a deficit.
Safe Weight Loss Rate
The Centers for Disease Control and Prevention (CDC) recommends losing 1-2 pounds per week for safe, sustainable weight loss. Faster weight loss can cause:
- Muscle loss (not just fat loss)
- Nutrient deficiencies
- Metabolic slowdown (adaptive thermogenesis)
- Gallstones
- Fatigue and mood changes
For most people, a daily deficit of 500-750 calories is ideal. Very low-calorie diets (below 1,200 calories for women or 1,500 for men) should only be done under medical supervision.
Weight Loss and Metabolic Adaptation
The 3,500-calorie rule is a simplified model. In reality, your body adapts to calorie restriction by slowing your metabolism (metabolic adaptation or "adaptive thermogenesis"). As you lose weight:
- Your BMR decreases (less body mass = fewer calories burned at rest)
- Non-exercise activity thermogenesis (NEAT) may decrease unconsciously
- Your body becomes more metabolically efficient
Recalculate your daily calorie target every 10-15 pounds lost to maintain a consistent deficit.
Using MyPlate for Weight Loss
The MyPlate: Calorie Deficit App can log meals toward the daily target from this page. Free to download, try every feature free. 3-day free trial. The calorie deficit calculator and TDEE calculator use the same maintenance math.
References
- NHS — Tips to help you lose weight (aim for 0.5 to 1 kg, or 1 to 2 lb, a week)
- MedlinePlus — Diet for rapid weight loss (usual low-calorie diets: about 1,200–1,500 kcal for women and 1,500–1,800 kcal for men)
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-7.
- NIH — Overweight & Obesity Statistics
Frequently asked questions
How does the weight loss calculator work?
The weight loss calculator estimates when you will reach your goal weight based on your current weight, goal weight, and daily calorie deficit. It uses the 3,500-calorie rule: one pound of fat equals approximately 3,500 calories. A 500-calorie daily deficit equals about 1 lb of weight loss per week.
What is a safe rate of weight loss?
The CDC recommends losing 1-2 pounds per week for safe, sustainable weight loss. This requires a daily calorie deficit of 500-1,000 calories. Faster weight loss can lead to muscle loss, nutrient deficiencies, and metabolic slowdown.
Is the 3,500-calorie rule accurate?
The 3,500-calorie rule is a simplified estimate. In practice, weight loss slows over time as your body adapts (metabolic adaptation). The calculator provides a general timeline; actual results vary by individual metabolism, activity, and adherence.
Should I adjust my calorie intake as I lose weight?
Yes. As you lose weight, your basal metabolic rate (BMR) and total daily energy expenditure (TDEE) decrease because your body requires fewer calories to maintain a lower weight. Recalculate your daily calorie target every 10-15 lbs lost.