Gastric Sleeve Weight Loss Calculator

How excess weight loss is calculated

The primary metric in bariatric surgery outcomes is percentage excess weight loss (%EWL). Excess weight is defined as the difference between your current weight and your ideal body weight (IBW), calculated here using the Hamwi formula. %EWL represents the proportion of that excess weight lost at each milestone.

Published sleeve gastrectomy data consistently show approximately 30% EWL at 3 months, 50% at 6 months, 65% at 12 months, and a plateau around 68% at 18–24 months. These are medians from large cohort studies; individual outcomes vary considerably depending on dietary adherence, activity level, and metabolic factors.

Weight loss phases after sleeve surgery

The first 6 months post-surgery are the rapid weight loss phase, during which restriction is greatest and hormonal changes (particularly reduced ghrelin production) suppress appetite most strongly. The 6–18 month period is a slower phase of continued loss with dietary quality becoming the primary determinant of continued progress. After 18 months, weight maintenance and avoiding regain are the primary goals.