Weight Loss Calculator

Follow these steps to calculate your personalized weight loss timeline:

1. Enter your current weight in pounds. Use a recent morning measurement taken after using the bathroom and before eating for the most accurate baseline. Body weight can fluctuate by 2 to 5 pounds throughout the day due to food, water, and sodium intake.
2. Enter your target weight in pounds. Set a realistic goal. If you have a large amount of weight to lose, consider setting intermediate goals of 10 to 20 pounds at a time. This keeps the timeline manageable and provides milestones to celebrate along the way.
3. Enter your height, age, and gender. These values are used in the Mifflin-St Jeor equation to calculate your Basal Metabolic Rate, which represents the calories your body burns at complete rest to maintain basic functions like breathing, circulation, and cell production.
4. Select your activity level. Be honest with this selection, as it significantly affects your TDEE calculation. Sedentary means a desk job with little movement. Light activity means exercise one to three days per week. Moderate means three to five days. Active means six to seven days. Very active means intense daily training or a physically demanding job.
5. Choose your weekly weight loss goal. Options range from 0.5 to 2 pounds per week. A rate of 1 pound per week requires a 500-calorie daily deficit and is sustainable for most people. Choosing 2 pounds per week requires a 1,000-calorie deficit, which may be too aggressive for smaller or less active individuals.

Review the results to see your projected target date, daily calorie intake target, and total daily energy expenditure. Never let your daily intake target fall below 1,200 calories for women or 1,500 calories for men without medical supervision.

A weight loss calculator projects how long it will take to reach your target weight based on your current body metrics, activity level, and desired weekly weight loss rate. At its core, weight loss is governed by the principle of energy balance: when you consistently consume fewer calories than your body expends, it draws on stored energy reserves, primarily body fat, to make up the difference. This sustained caloric deficit is the fundamental mechanism behind all successful weight loss approaches, regardless of the specific diet or exercise program followed.

The commonly cited rule that 3,500 calories equals one pound of body fat provides a useful approximation for planning purposes. However, this figure is a simplification. The actual caloric content of adipose tissue varies because body fat is not pure lipid. It contains water, connective tissue, and cellular components. Additionally, as you lose weight, your body does not exclusively burn fat. Some lean tissue is also lost, and the ratio depends on factors like protein intake, resistance training, and the size of the caloric deficit. Larger deficits tend to result in greater lean tissue loss, which is one reason moderate deficits are recommended.

Medical professionals and nutrition researchers generally agree that a safe and sustainable rate of weight loss is one to two pounds per week, corresponding to a daily deficit of 500 to 1,000 calories. Losing weight faster than this increases the risk of muscle loss, nutrient deficiencies, gallstones, and metabolic slowdown. Metabolic adaptation is a well-documented phenomenon in which the body reduces its energy expenditure in response to prolonged caloric restriction. Your basal metabolic rate can decrease by 10 to 15 percent beyond what weight loss alone would predict, making continued weight loss progressively more difficult.

Set point theory suggests that the body has a preferred weight range that it defends through hormonal signals affecting hunger and metabolism. While this does not mean weight loss is impossible, it helps explain why maintaining weight loss long-term can be challenging and why gradual, sustainable approaches that emphasize lifestyle changes rather than extreme restriction tend to produce the best long-term outcomes. Combining a moderate caloric deficit with regular physical activity, adequate protein intake, and sufficient sleep creates the most favorable conditions for lasting weight loss.

The calculator uses the Mifflin-St Jeor equation and energy balance principles:

Step 1 — Basal Metabolic Rate (BMR):

• Male: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
• Female: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161

Step 2 — Total Daily Energy Expenditure (TDEE): TDEE = BMR × Activity Multiplier

Step 3 — Deficit and Timeline:

• Daily Deficit = (Weekly Goal in lbs × 3,500) ÷ 7
• Daily Calorie Intake = TDEE − Daily Deficit
• Days to Goal = (Current Weight − Target Weight) × 3,500 ÷ Daily Deficit

Note that this calculator uses your current weight for all projections. In reality, as you lose weight your TDEE decreases, meaning progress may slow over time. Recalculate every 10 to 15 pounds lost to update your targets.

Example 1 — Moderate Loss at 1 lb/week: A 200-pound male, age 30, height 5'10" (70 inches), with moderate activity wants to reach 180 lbs. Weight in kg = 90.7. Height in cm = 177.8. BMR = (10 × 90.7) + (6.25 × 177.8) − (5 × 30) + 5 = 907 + 1,111 − 150 + 5 = 1,873 calories. TDEE = 1,873 × 1.55 = 2,903 calories. For 1 lb/week loss, daily deficit = 500 calories. Daily intake target = 2,903 − 500 = 2,403 calories. Weight to lose = 20 lbs. Days to goal = (20 × 3,500) ÷ 500 = 140 days, or 20 weeks (approximately 5 months). This is a comfortable deficit that allows for satisfying meals while steadily losing weight.

Example 2 — Conservative Loss at 0.5 lb/week: A 150-pound female, age 45, height 5'4" (64 inches), with light activity wants to reach 140 lbs. Weight in kg = 68.0. Height in cm = 162.6. BMR = (10 × 68) + (6.25 × 162.6) − (5 × 45) − 161 = 680 + 1,016 − 225 − 161 = 1,310 calories. TDEE = 1,310 × 1.375 = 1,801 calories. For 0.5 lb/week loss, daily deficit = 250 calories. Daily intake target = 1,801 − 250 = 1,551 calories. Weight to lose = 10 lbs. Days to goal = (10 × 3,500) ÷ 250 = 140 days, or 20 weeks. The slower rate is more appropriate here because a larger deficit would push daily intake uncomfortably close to 1,200 calories, which could be difficult to sustain and may not provide adequate nutrition.

Example 3 — Aggressive Loss at 2 lbs/week: A 250-pound male, age 35, height 6'0" (72 inches), with sedentary activity wants to reach 210 lbs. Weight in kg = 113.4. Height in cm = 182.9. BMR = (10 × 113.4) + (6.25 × 182.9) − (5 × 35) + 5 = 1,134 + 1,143 − 175 + 5 = 2,107 calories. TDEE = 2,107 × 1.2 = 2,528 calories. For 2 lbs/week loss, daily deficit = 1,000 calories. Daily intake target = 2,528 − 1,000 = 1,528 calories. Weight to lose = 40 lbs. Days to goal = (40 × 3,500) ÷ 1,000 = 140 days, or 20 weeks. While 2 lbs/week is aggressive, this individual's higher TDEE means the daily intake target of 1,528 calories is still above the minimum recommended threshold. As weight decreases toward the goal, recalculating is essential because TDEE will drop and the same deficit may become unsustainable.