Gastric Bypass Weight Loss Calculator

The Gastric Bypass Weight Loss Calculator estimates your projected weight based on inputs like current body stats, activity level, and chosen time frame. This tool helps bariatric surgery candidates and post-operative patients visualize potential outcomes and plan for a healthier future. Whether you are estimating results for 6 months or setting a 2-year goal, this calculator offers the data you need to stay motivated.

Enter your current weight in pounds (lbs)
Enter your height in inches (e.g., 67 for 5'7")
Enter your current age in years
Enter your goal weight in pounds (optional)
1=Sedentary, 2=Lightly active, 3=Moderately active, 4=Very active, 5=Extremely active

How Projected Weight Is Calculated

Projected weight is calculated by estimating how much of your excess body weight you are likely to lose over a specific period. Standard bariatric algorithms suggest that patients lose a specific percentage of their excess weight, which varies by the time elapsed since surgery.

Projected Weight = Current Weight - (Excess Weight × EWL %)

Where:

  • Excess Weight = Current Weight - Ideal Body Weight
  • EWL % = Expected Excess Weight Loss percentage for time frame

First, we determine your ideal body weight based on your height and gender. Then, we calculate your total excess weight and apply a standard loss percentage for 6 months, 1 year, or 2 years. Finally, we adjust the result based on your activity level and diabetes status to refine the accuracy.

What Your Projected Weight Means

This number represents a realistic estimate of where your weight might stabilize at a specific point in your post-surgery journey. It helps you set achievable milestones rather than aiming for instant perfection.

Short-Term Planning (6 Months)

If your projected weight shows a significant drop, you are likely on track with the typical "honeymoon phase" of rapid weight loss. Use this milestone to validate your dietary adherence.

Long-Term Goals (2 Years)

Most patients reach their maximum weight loss around the 2-year mark. If this number aligns with your personal goal weight, you are within the standard success range for bariatric procedures.

Pro Tip

Recalculate your projection every 3 to 6 months using your updated current weight to see if you are keeping pace with the average timeline.

Disclaimer: This calculator is for informational purposes only and does not constitute medical advice. Surgical results vary significantly based on individual health factors and adherence to lifestyle changes. Always consult your bariatric surgeon or healthcare provider for personalized medical guidance.