Simple BMI
Press Calculate or Enter to see results. Clear starts a new patient.
Bariatric procedure diagrams
Tap a diagram to open it full size.
Other bariatric calculators
MBSAQIP Bariatric Surgical Risk/Benefit Calculator (ACS)30-day complications, 1-year weight curve, diabetes / BP / sleep apnea remission
Individualized Metabolic Surgery (IMS) ScoreDiabetes severity to help choose sleeve vs bypass (Cleveland Clinic)
Cleveland Clinic risk calculator libraryIncludes 10-year diabetes complication risk with vs without surgery (also the BariatricCalc app)
STOP-BangSleep apnea screening
Other non-bariatric calculators
ACS NSQIP Surgical Risk Calculator30-day risks for almost any operation, by procedure code
Caprini score (MDCalc)Blood clot (VTE) risk and prophylaxis
Revised Cardiac Risk Index (MDCalc)Cardiac complications after noncardiac surgery
Gupta MICA (MDCalc)Heart attack or cardiac arrest after surgery
ARISCAT (MDCalc)Lung complications after surgery
CeDAR: Ventral Hernia (iPhone app)Wound complication risk and cost after ventral hernia repair
Treatment criteria
Criteria for treatment with / without weight-related comorbidity
MedicationDM2, or BMI ≥ 27 / 30
SurgeryBMI ≥ 30 / 35
Supporting guidelines and trials
All adultsSurgery for BMI ≥ 35 regardless of comorbidity; consider BMI 30–34.9 with metabolic disease.
- Eisenberg D, et al. 2022 ASMBS and IFSO indications for metabolic and bariatric surgery. Surg Obes Relat Dis 2022. doi
Type 2 diabetesMetabolic surgery for BMI ≥ 30 (≥ 27.5 in Asian Americans) who are good surgical candidates.
Asian ancestryLower BMI cut-offs: obesity from BMI ≥ 25, surgery considered from BMI ≥ 27.5.
- WHO Expert Consultation. Appropriate body-mass index for Asian populations. Lancet 2004;363:157–163. doi
- ASMBS/IFSO 2022 and ADA 2026, above.
MedicationBMI ≥ 30, or ≥ 27 with a weight-related condition.
- Grunvald E, et al. AGA guideline on pharmacological interventions for adults with obesity. Gastroenterology 2022;163:1198–1225. doi
- Wilding JPH, et al. Semaglutide 2.4 mg in adults with overweight or obesity (STEP 1). N Engl J Med 2021;384:989–1002. doi
- Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med 2022;387:205–216. doi
AdolescentsSurgery for BMI ≥ 35 (or 120% of the 95th percentile) with a major comorbidity, or ≥ 40 (140%).
- Hampl SE, et al. AAP clinical practice guideline for children and adolescents with obesity. Pediatrics 2023;151:e2022060640. doi
- ASMBS/IFSO 2022, above.
Beyond BMIDiagnose "clinical obesity" from excess fat plus organ or functional effects, not BMI alone.
- Rubino F, et al. Definition and diagnostic criteria of clinical obesity (Lancet Commission). Lancet Diabetes Endocrinol 2025. doi
About the weight-loss estimates
The typical weight loss after sleeve (LSG) and bypass (RYGB) uses median % total weight loss (%TWL) from the PCORnet bariatric study, with interquartile ranges (IQR, the middle half of patients) from SOPHIA.
Between 1 and 5 years the calculator estimates in a straight line between these values. They reflect outcomes before GLP-1 medications were widely used, and individual results vary.
Links
Videos
Contact card for MGH patients
Massachusetts General Hospital
Weight Center (Surgery)
Bariatric Surgery RNMonday–Friday, 9:00am–4:30pm
617-643-6150
After hours, weekends & holidaysCall the hospital operator and ask them to page the bariatric surgeon on call, page #20377
617-726-2000
Weight Center Surgical CoordinatorMonday–Friday, 8:00am–4:30pm
617-643-4002
Hernia and foregut
