Gastric Sleeve Weight Loss Calculator — Expected Outcome Timeline
Estimate your expected weight at 3, 6, 12, 18, 24, 36 and 60 months after gastric sleeve surgery, based on median Excess Weight Loss percentages from published clinical research. Enter your current weight and height to see a projected timeline.
Unit system
kg
cm
Median outcome: 65% of excess weight lost by 12 months. Individual results vary widely.
- 1
Ideal weight (BMI 25)
25 × 1.7² m² = 72.3 kgWeight corresponding to BMI 25 at this height; used to define excess weight. - 2
Excess weight
120 − 72.3 = 47.8 kg - 3
12-month weight loss (65% EWL)
65% × 47.8 = 31 kgMedian 65% excess weight loss at 12 months from published clinical meta-analyses. - 4
Expected weight at 12 months
120 − 31 = 89
How does this calculator work?
After gastric sleeve surgery the median excess weight loss is ~40% by 3 months, ~65% by 12 months (typical peak), and ~55% at 5 years. Excess weight = current weight minus weight at BMI 25. These are population medians from published clinical data; individual outcomes vary substantially based on starting BMI, age, and adherence.
Formula
How this is calculated
Gastric sleeve surgery (sleeve gastrectomy) removes roughly 75–80% of the stomach, limiting food intake and reducing ghrelin (the primary hunger hormone). Results are reported as Excess Weight Loss percentage (EWL%), where excess weight is the gap between your current weight and an ideal weight at BMI 25 — the reference used in the majority of bariatric surgical research and by ASMBS/IFSO guidelines.
The EWL% milestones used here — 40% at 3 months, 58% at 6 months, 65% at 12 months, 68% at 18 months, and gradual settling to ~55% at 5 years — represent population medians pooled from systematic reviews published between 2015 and 2023. The 12-month period typically marks near-peak weight loss; some regain after 18–24 months is expected and well-documented. The ideal weight is calculated as 25 × height² (m²), which is the standard BMI-25 body weight.
This tool is an educational estimator, not a medical prediction. Actual outcomes vary substantially based on starting BMI, age, sex, adherence to post-operative dietary guidelines, physical activity, and whether comorbidities like type 2 diabetes are present. Consult a qualified bariatric surgeon and dietitian for personalised expectations.
Frequently asked questions
Most patients lose 55–70% of their excess weight (the amount above BMI 25) within 12–18 months. The population median at 12 months is about 65% EWL from published meta-analyses. Results vary significantly: patients with lower starting BMI, younger age, and strong dietary adherence often exceed the median; those with very high BMI or metabolic comorbidities may lose less.
EWL% measures what fraction of the weight above BMI 25 has been lost. Excess weight = current weight − (25 × height² in m²). If your excess weight is 50 kg and you lose 32.5 kg, your EWL% is 65%. It normalises for starting BMI, making comparisons across patients more meaningful than total weight lost.
Yes. Some regain after the 18–24-month nadir is normal and expected. Long-term (5-year) data typically shows EWL% settling around 50–60%, down from the ~68% peak. Maintaining the post-operative diet, staying active, and attending follow-up care are the strongest predictors of long-term success.
Also known as
TG we-Calculate Editorial Team. (2026). Gastric Sleeve Weight Loss Calculator — Expected Outcome Timeline [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/gastric-sleeve-weight-loss-calculator
TG we-Calculate Editorial Team. "Gastric Sleeve Weight Loss Calculator — Expected Outcome Timeline." TG we-Calculate. 2026. https://we-calculate.com/calculator/gastric-sleeve-weight-loss-calculator.
TG we-Calculate Editorial Team, "Gastric Sleeve Weight Loss Calculator — Expected Outcome Timeline," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/gastric-sleeve-weight-loss-calculator
@misc{wecalculate_gastric_sleeve_weight_loss_calculator, title = {Gastric Sleeve Weight Loss Calculator — Expected Outcome Timeline}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/gastric-sleeve-weight-loss-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?