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BMI Calculator for Bariatric Surgery Candidates

Body Mass Index (BMI) is a simple tool used to estimate body fat based on height and weight. It’s an important first step in determining whether you may qualify for weight-loss surgery at the BASS Bariatric Surgery Center.

Calculate Your BMI





What Is BMI and Why Does It Matter?

BMI is a mathematical formula:

weight (lbs) ÷ height² (inches) × 703‍

It provides a quick way to classify your weight status:

  • Underweight: BMI < 18.5
  • Normal weight: BMI 18.5–24.9
  • Overweight: BMI 25–29.9
  • Obesity Class I: BMI 30–34.9
  • Obesity Class II: BMI 35–39.9
  • Obesity Class III: BMI ≥ 40

A BMI of 35 or higher may indicate that you qualify for bariatric surgery, especially if you also have health conditions related to obesity.

Color-coded BMI chart showing height on Y-axis, weight on X-axis, and BMI categories such as underweight, normal weight, overweight, and obesity.

Health Risks of a High BMI

According to the CDC, over one-third of U.S. adults are obese — and obesity increases the risk for many chronic health conditions, including:

  • Type 2 Diabetes
  • Heart Disease
  • High Blood Pressure
  • Sleep Apnea
  • Osteoarthritis
  • GERD (acid reflux)
  • Fatty Liver Disease
  • Depression

Is BMI Always Accurate?

While BMI is a helpful screening tool, it isn’t perfect. It doesn’t distinguish between fat and muscle. That means:

  • Athletes may have a high BMI due to muscle, not fat.
  • Older adults may have a normal BMI but still carry excess fat.

That’s why we also recommend tracking waist circumference for a more complete picture.

How to Measure Waist Circumference

  1. Place a tape measure above your hip bones.
  2. Make sure it’s level and snug — but not tight.
  3. Measure after exhaling naturally.

High abdominal fat increases the risk for heart disease and diabetes, even in people with a normal BMI.

Person adjusting balance scale at doctor’s office, showing step in calculating BMI during a medical weight assessment.

Are You a Candidate for Bariatric Surgery?

You may qualify for bariatric surgery if you:

  • Have a BMI of 40 or higher, or
  • Have a BMI of 35+ with obesity-related health issues
  • Are 100 pounds or more over your ideal body weight
  • Have been unable to lose weight through diet and exercise
  • Are between the ages of 14 and 75

If weight gain is due to a temporary condition (like pregnancy), you may not be eligible.

Why Choose Surgery Over Diets or Injections?

Bariatric surgery is a proven long-term solution. Our experienced team offers:

  • Gastric Sleeve
  • Gastric Bypass
  • Duodenal Switch
  • Adjustable Gastric Band

These procedures can eliminate or improve diabetes, high blood pressure, sleep apnea, and more — all while helping you regain confidence and mobility.

We do not recommend or prescribe weight-loss injections like semaglutide due to safety concerns.

Start Your Journey Today

Request a Consultation with one of our expert bariatric surgeons in Walnut Creek or Brentwood.

Is Weight-Loss Surgery Right For You?

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Patient Success Stories

Bariatric Surgery & Obesity Specialists | Weight-Loss Surgery Center clinics in Walnut Creek and Brentwood California
Before Surgery
After Surgery

My Weight-Loss Surgery Success Story

My name is Denise. I started my weight-loss journey in December of 2014 by visiting Dr. Chin. It was ten months of doctors’ appointments, weigh-ins, and medical tests. But I was focused and determined. Finally, my surgery date came. I was sleeved in October 2015, and it was the best decision I have ever made for myself. I was 57 years old at the time. I asked my surgeon, Dr. Chin, if I was too old for the surgery, and he said, “No one is too old to get healthy.” He was so very right. I was 310 pounds at my heaviest, pre-surgery. I was pre-diabetic, and had high blood pressure. My back, knees, and ankles hurt most of the time, and I was always short of breath. Those were just the medical conditions I had because of my weight. I was self-conscious and depressed. I was very unhappy. Surgery was a piece of cake (no pun intended). I was walking on the treadmill within two days. Soon, I was amazed at the transformation I was having, both in my weight loss and with my attitude towards food. As the weight loss kept happening, I was gaining my health back. I am no longer on blood pressure medicine, and I am no longer pre-diabetic. My knees, back, and ankles don’t hurt anymore because I am not carrying so much weight. I can walk and move around without being short of breath. My confidence has returned, and I am so much happier now that I am 100 pounds lighter. I swim a mile five days a week, and walk three to four miles every day, and I enjoy it. There are so many accomplishments that have come from losing weight like shopping in the regular size section, fitting in any chair, crossing my legs, not having to ask for an extension on the airplane, and the list goes on. The only regret I have is not having this surgery sooner. I would like to thank Dr. Chin and all of the staff involved in my life saving/changing surgery.

Denise Brown
Past Bariatric Surgery Patient

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Gastric Sleeve Surgery Helps Patient Lose 120 Pounds and Kick Diabetes

Gastric Sleeve Surgery Saved My Life

57-year-old Gastric Sleeve Patient Drops 100 Pounds After Surgery

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BASS Medical Group Walnut Creek CA

Meet our Bariatric Surgeons

Bariatric Surgery Specialists | Weight Loss Surgery Center in Walnut Creek and Brentwood
bariatric weight-loss doctor brian t. chin

Brian T. Chin, MD, FACS

Bariatric Surgeon

Doctor Biography

Dr. Brian Chin was born and raised in the Bay Area. After graduating from Acalanes High School in Lafayette he ventured cross-country to coastal Maine, where he graduated magna cum laude from Bowdoin College with a bachelor’s degree in physics and mathematics. From there, he went on to earn a master’s degree in applied physics from Columbia University. He earned his medical degree at the University of Michigan Medical School, then returned to California for his surgery residency at the University of California at San Diego, where he won the Department of Medicine’s Halasz Award for surgical consultation and the Department of Surgery’s Chairman’s Prize for teaching and service excellence. Additionally, he served as administrative chief resident. Following residency, Dr. Chin completed a fellowship in bariatric and advanced laparoscopic surgery at the University of California at San Francisco, working alongside world-renowned leaders at the forefront of laparoscopic surgery. Dr. Brian Chin is board certified in surgery by the American Board of Surgery and in advanced trauma life support by the American College of Surgeons. Dr. Chin also serves as a trauma surgeon at the John Muir Medical Center, which is certified as a level II trauma center by the American College of Surgeons and is Contra Costa County’s only trauma center. He sees patients in Walnut Creek and Brentwood.

bariatric weight-loss doctor jason f. moy

Jason F. Moy, MD, FACS

Bariatric Surgeon

Doctor Biography

Dr. Jason Moy is a graduate of the University of Michigan, where he earned both his undergraduate degree from the Honors College and Master of Public Health degree in molecular epidemiology from the School of Public Health. Dr. Moy received his medical degree from Michigan State University. Following medical school, he completed a surgical residency at William Beaumont Hospital. There, in addition to surgical training, Dr. Moy was extensively involved in surgical research and had the opportunity to both publish peer-reviewed articles and present at national and international surgical meetings. After completing residency, Dr. Moy continued his surgical training in New York City as a fellow in minimal access and bariatric surgery in a joint program with Cornell Medical College and Columbia University at New York Presbyterian Hospital. In New York, Dr. Moy trained with pioneers in laparoscopic and bariatric surgery, Drs. Michel Gagner, Alfons Pomp and Dennis Fowler. He also continued surgical research, publishing multiple times, including a paper on laparoscopic sleeve gastrectomy technique. At Columbia, Dr. Moy was appointed a clinical instructor of surgery. Dr. Moy is an advanced laparoscopic surgeon, practicing the full scope of general surgery, bariatric surgery, and trauma surgery.