How does this weight loss calculator work?+
This calculator uses the Mifflin-St Jeor formula to estimate your basal metabolic rate (BMR), then multiplies by an activity factor to get your total daily energy expenditure (TDEE). It then subtracts daily calorie deficits of 250, 500, 750, and 1,000 calories to show how quickly you will reach your target weight at each pace. One pound of body fat equals about 3,500 calories, so a 500-calorie daily deficit leads to about 1 pound of loss per week.
What is a safe rate of weight loss?+
Most medical professionals recommend losing 1-2 pounds per week for sustainable, healthy weight loss. Losing more than 2 pounds per week long-term can lead to muscle loss, nutritional deficiencies, gallstones, and a slowed metabolism. The calculator warns you if a deficit would put your daily intake below 1,200 calories (women) or 1,500 calories (men), which are generally considered the minimum safe intake without medical supervision.
What is the Mifflin-St Jeor formula?+
The Mifflin-St Jeor formula is the most widely recommended equation for estimating basal metabolic rate (BMR). For men: BMR = 10 x weight (kg) + 6.25 x height (cm) - 5 x age - 5. For women: BMR = 10 x weight (kg) + 6.25 x height (cm) - 5 x age - 161. Research shows it predicts actual resting metabolic rate within 10% for most people, making it more accurate than the older Harris-Benedict formula.
Why does my weight loss slow down over time?+
As you lose weight, your body needs fewer calories to maintain itself, meaning your TDEE decreases. This is called metabolic adaptation. A deficit that initially caused 2 pounds of loss per week may only produce 1 pound per week after significant weight loss. To keep losing at the same rate, you need to further reduce calories or increase physical activity. This calculator uses your current weight for estimates, so recalculate regularly as you progress.
How should I split macros for weight loss?+
When losing weight, higher protein intake helps preserve muscle mass and keeps you feeling full. A common recommendation is 30% of calories from protein, 35% from carbohydrates, and 35% from fat. This calculator provides macronutrient targets in grams for each deficit level. Protein and carbs provide 4 calories per gram, while fat provides 9 calories per gram. Adjust the ratio based on your preferences and body response.
Is eating below 1,200 or 1,500 calories safe?+
Going below 1,200 calories (women) or 1,500 calories (men) per day long-term is generally not recommended without medical supervision. Very low-calorie diets can lead to nutritional deficiencies, muscle loss, fatigue, hair loss, and metabolic adaptation that makes future weight loss harder. If the calculator shows your target falling below these thresholds, consider a more moderate deficit combined with increased physical activity.