In addition to showing you how to calculate your BMI, this page will cover why your score is important and the background of the BMI formula.
Click Here to See Your BMITABLE OF CONTENTS
Click on any of the topics below to jump directly to that section

SECTION SUMMARY:
- How to use the BMI formula
- The BMI classifications are Overweight, Severely Obese, Morbidly Obese, and Super Obese
How to Calculate BMI Using the BMI Formula
Body mass index is a measure of your weight’s relation to your height. Here’s the BMI formula for pounds/inches and kilograms/meters…
or
BMI (kg/m) = weight / height2
BMI Classifications & How to Interpret Them
Your BMI score can be used to classify your weight status. But don’t take your “classification” too seriously just yet. Moderately overweight people actually live longer than those at “normal” weight (2).
And, by the way, we take issue with the concept of “normal” as determined by classifications like the BMI classifications. So while giving you some idea of where you are with your weight, don’t focus on it too much. Everyone has a different body, and there is not a “one-size-fits-all” body type. These weight classifications (i.e. “healthy weight”) is one example of the many discriminatory challenges the overweight face on a daily basis. More on this can be found on our Obesity Discrimination page.
Tap here to see the weight classifications for adults and what they mean for bariatric surgery
Classification* | Body Mass Index (BMI) |
---|---|
Underweight | Below 18.5 |
Healthy Weight | 18.5 – 24.9 |
Overweight | 25.0 – 29.9 |
Obesity Class I (“Obese”) (maybe eligible for bariatric surgery) | 30.0 – 34.9 |
Obesity Class II (“Severely Obese”) (maybe eligible for bariatric surgery) | 35.0 – 39.9 |
Obesity Class III (“Morbidly Obese”) (maybe eligible for bariatric surgery) | 40.0 – 49.9 |
Obesity Class IV (“Super Obese”) (maybe eligible for bariatric surgery) | Over 50.0 |
*Applies to adults over the age of 19 |
In addition to the questionable names applied to the above classes, the BMI rating system has other limitations…
- It doesn’t take into account the fact that muscle weighs more than fat, so it overestimates body fat in muscular people and underestimates body fat for people with less muscle mass.
- Fat around the midsection is worse than fat that is evenly dispersed throughout the body. For example, men with a waist circumference over 40 inches and women with a waist circumference over 35 inches have a increased risk of cardiovascular disease compared to people with the same BMI but a smaller waist circumference.
- The same BMI formula is applied to both men and women despite the inherent differences in body fat between them (men’s average BMI is 27.8 while women are at 26.8). For example, women tend to have a slightly higher percentage of body fat and men tend to be slightly heavier relative to their height because of a higher relative muscle mass. Because of this, not having a formula that takes into account gender skews the results, making them less accurate.
Despite its shortcomings, knowing how to calculate your BMI is a decent first step in determining which health issues you could be at risk for. As we’ll get into below, it’s also an essential component of getting insurance approval for bariatric surgery.
In general, you should be concerned about obesity health problems if your BMI is 30 or more or if your BMI is between 25 and 29.9 and you have two or more of the following…
- Cigarette smoking
- Family history of premature heart disease
- High blood glucose (blood sugar)
- High blood pressure (hypertension)
- Low HDL-cholesterol (“good” cholesterol)
- High LDL-cholesterol (“bad” cholesterol)
- High triglycerides
- Physical inactivity (3)
Your doctor will also know how to calculate BMI and will interpret your score along with results from several other tests to diagnose your obesity class and confirm its potential health impacts. If you doubt your BMI score and would like to cross-reference it with another at-home test, see our How to Calculate Body Fat Percentage page.
SECTION SUMMARY:
- You must have a BMI of 30+ and weight-related health issues; or
- A BMI of 40+ (health issues not required) to qualify for weight loss surgery
If your body mass index is above 30, you may qualify for one of the following types of weight loss surgery.
Tap here to expand a chart explaining BMI qualifications for weight loss surgery.
Body Mass Index | Health Problems Required to Qualify |
---|---|
30 to 34.9 | May qualify for Gastric Balloon. This BMI range may also qualify for other procedures if the patient has poorly controlled diabetes or metabolic syndrome. |
35 to 40 | May qualify for Gastric Balloon. This BMI range may also qualify for other procedures if the patient has poorly controlled type 2 diabetes, a higher risk of cardiovascular disease, or suffers from another weight-related health issue. |
40.1 to 45 | May qualify for any weight loss procedure other than Gastric Balloon. |
45.1 to 55 | May qualify for any weight loss procedure other than Gastric Balloon. |
Above 55 | May qualify for any weight loss procedure other than Gastric Balloon or AspireAssist. |
These qualifications apply for most countries and most procedures, including the U.S., Canada, Australia, and the U.K.
Assuming your BMI qualifies, your next step is to decide which procedures may be a fit for you.
Or you can continue to learn more about body mass index below.

SECTION SUMMARY:
- BMI is easy to calculate
- The BMI calculation correlates with risk levels
In 1998, the National Institutes of Health (NIH) brought together an expert panel who recommended that body mass index be used to determine whether an individual is overweight or obese.
In addition to being a fast, easy, and cheap measurement, the panelists felt that for most people, BMI was a good representation of body fat. They also saw that it directly correlated with the risk of death and several diseases and conditions, including…
- Adult-onset asthma
- Arthritis
- Breathing problems
- Coronary heart disease
- Hypertension
- Ovarian cancer
- Total and ischemic stroke
See our Obesity Health Problems page for a full list of weight-related conditions.
SECTION SUMMARY:
- BMI for kids and teens is different than for adults
- The classification for 'Obese' is defined as 95th+ percentile
Children and teenagers up to 19 years of age use a different body mass index labeling system than adults (4). In this system, percentiles are used that take into account the child’s age.
Tap here to to learn BMI classifications for children and teenagers up to 19 years old
In children and teens from 6 to 19 years, BMI is age and gender specific. In other words, a 10 year old male will have a different “normal” BMI than a 15 year old female. Being “overweight” means having a BMI at or above the 95th percentile in their specific age/gender category.
See the CDC’s individual and clinical growth charts to learn where you (or your child) fall.
Also see our Teen Obesity & Adolescent Bariatric Surgery page for more information about obesity in young people and the appropriateness of weight loss surgery for teens.
SECTION SUMMARY:
- You can ask a local bariatric practice for a free insurance check or cost quote
- You can attend a free in-person seminar or an online webinar offered by a local weight loss surgeon
- You should schedule a phone or in-person consultation (both often free), if you are interested in learning more about weight loss surgery
Find a Bariatric Surgeon
Find a Bariatric Surgeon
Back to PageDo You Qualify for a Bariatric Procedure?
Do You Qualify for a Bariatric Procedure?
Back to PageDo You Qualify for a Bariatric Procedure?
Patients who qualify for bariatric surgery usually:
- Are at least 80 lbs (36 kg) overweight
- Are between 18 and 75 years old
- Have a history of failed weight loss attempts (e.g., failed diets)
- Thoroughly understand that the procedure is just a tool; long-term success requires significant diet and lifestyle changes
The minimum bariatric surgery qualifications include:
- A body mass index (BMI) of 40 or more
- OR a BMI between 30 and 39.9 with a serious obesity-related health problem like diabetes, high blood pressure, sleep apnea, high cholesterol, joint problems, or others
- OR a BMI of 30 to 40 with or without health issues for the gastric balloon procedure
To calculate your BMI, enter your height and weight into the tool, then click the “Calculate BMI” button.
Click here to learn moreCheck My Insurance Tool
Check My Insurance Tool
Back to PageCheck My Insurance Tool
Bariatric surgery insurance coverage varies by insurance policy:
Individual/Family Plans & Small Group Plans – Coverage varies by state; coverage is required by the Affordable Care Act in some states
Large Group Plans – Coverage depends on whether your employer has chosen to add it to your policy
Medicare and Medicaid – Bariatric surgery is covered
If your policy covers it and you meet the qualification requirements, your plan will likely include 4 procedures:
- Gastric sleeve
- Gastric bypass
- LAP-BAND®
- Duodenal switch
Your surgeon may be able to get partial coverage for the other procedures.
Use the tool to find out if your insurance covers bariatric surgery.
Click here to learn moreBariatric Surgery Weight Loss Estimator Tool
Bariatric Surgery Weight Loss Estimator Tool
Back to PageBariatric Surgery Weight Loss Calculator
You will start losing weight fast after any bariatric surgery procedure, but the total amount lost varies based on:
- The procedure you choose
- How closely you follow your doctor’s instructions
Enter your information into the tool to get an idea about how much weight you’ll lose after each procedure.
Bariatric Procedure Cost Compare Tool
Bariatric Procedure Cost Compare Tool
Back to PageBariatric Procedure Cost Compare Tool
Your out-of-pocket bariatric surgery cost can range anywhere from $0 to $20,000 or more depending on several factors, including:
Whether your insurance covers it – many insurances (including Medicare, Medicaid, and many individual/family and employer-provided policies) cover the majority of costs for gastric sleeve, gastric bypass, LAP-BAND®, and duodenal switch. The other types of bariatric surgery are less likely to be covered, although you may be able to get insurance to pay for some of the costs. Tap the “With Insurance” button in the tool to see average out-of-pocket costs per procedure after insurance pays. See our Insurance Tool to find out if your plan covers it.
Which procedure you choose – if insurance won’t pay, costs range anywhere from $8,000 to $20,000+, depending on the procedure. Tap the “Without Insurance” button in the tool to compare the national average self-pay costs for each procedure. (NOTE: Some surgeons offer each procedure for as low as half of the national average).
How competitive your surgeon and hospital fees are – there is often a substantial difference in costs between different doctors and hospitals, even within the same town.
Whether you qualify for tax write-offs – Bariatric surgery is tax deductible, which can have a big impact on the total cost of surgery. You can deduct medical expenses if your out-of-pocket costs are more than 10% of your adjusted gross income. See our Tax Tool to find out if your bariatric procedure will be tax deductible.
How you choose to pay for your procedure – If insurance covers it, you’ll only be responsible for any copays, deductibles, and coinsurance required by your specific plan. If you pay for the procedure without insurance, total costs will depend on how you pay. For example, your surgeon may offer a discount if you pay the full amount up front, and you can make the costs more affordable by applying for bariatric surgery financing.
Click here to learn moreLOAN ESTIMATOR TOOL
LOAN ESTIMATOR TOOL
Back to PageBariatric Surgery Tax Write-Off Calculator
Weight loss surgery is tax deductible, which can have a big impact on the total cost of surgery. You can deduct medical expenses if the costs are more than 10% of your adjusted gross income.
Use the tool to find out if you qualify for a tax deduction.
To receive the deductions, you’ll need to complete Schedule A of the IRS Form 1040. You’ll also need to save your medical bills and payment statements as proof. Money in one of the following special savings accounts (or even your IRA) may also be a way to pay for part of surgery tax-free:
- Health Savings Account (HSA)
- Archer Medical Savings Account (Archer MSA)
- Health Reimbursement Account (HRA)
- Flexible Spending Account (FSA)
Bariatric Surgery Tax Write-Off Tool
Bariatric Surgery Tax Write-Off Tool
Back to PageBariatric Surgery Tax Write-Off Calculator
Weight loss surgery is tax deductible, which can have a big impact on the total cost of surgery. You can deduct medical expenses if the costs are more than 10% of your adjusted gross income.
Use the tool to find out if you qualify for a tax deduction
To receive the deductions, you’ll need to complete Schedule A of the IRS Form 1040. You’ll also need to save your medical bills and payment statements as proof.
Money in one of the following special savings accounts (or even your IRA) may also be a way to pay for part of surgery tax-free:
- Health Savings Account (HSA)
- Archer Medical Savings Account (Archer MSA)
- Health Reimbursement Account (HRA)
- Flexible Spending Account (FSA)
Bariatric Surgery Recovery Timeline Tool
Bariatric Surgery Recovery Timeline Tool
Back to PageBariatric Surgery Recovery Timeline Tool
Bariatric surgery recovery varies by procedure. Here are the ranges:
- Timeline Range: from 3 days to 6 weeks to full recovery
- Hospital Stay: from outpatient (return home same-day) to 3 days
- Back to Work: from 3 days to 3 weeks
- Pain Range: from mild discomfort to manageable with medication
- Diet Range: from no restrictions to slow transition from clear liquids to solid foods
- Activity Range: from no restrictions to slow transition back to regular activity and exercise
Use the tool to learn more about each stage of recovery.
Click here to learn moreBariatric Procedure Summaries
Below is a brief explanation of how each bariatric surgery procedure works. Tap the icons for more information.
Bariatric Procedure Summaries
Back to PageBelow is a brief explanation of how each bariatric surgery procedure works. Tap the icons for more information.
Bariatric Procedure Comparison Tool
Bariatric Procedure Comparison Tool
Back to PageBariatric Procedure Comparison Tool
There are 6 types of bariatric surgery (also called “weight loss surgery”) available, including:
- Gastric Sleeve – feel less hungry & full sooner while eating
- Gastric Bypass – feel full sooner while eating & absorb fewer minerals
- Duodenal Switch – feel less hungry & full sooner while eating, absorb fewer calories and minerals
- LAP-BAND® – feel full sooner while eating
- Gastric Balloon – temporarily feel full sooner while eating (balloon removed after 6 months)
- AspireAssist – drain a portion of stomach contents after eating
Use the tool to compare each procedure.
Click here to learn moreBariatric Surgery Quiz: Learn Your Top 2 Procedures
Bariatric Surgery Quiz: Learn Your Top 2 Procedures
Back to PageBariatric Surgery Quiz: Learn Your Top 2 Procedures
The best weight loss surgery options for you depend on:
- How much weight you want to lose
- Your current age, weight, health issues, habits, and lifestyle
- Your expectations for life after surgery
- Whether you want a reversible procedure
- What “trade-offs” you are willing to make
Take the quiz to find out which two procedures are best for you and why.
Bariatric Surgery Health Benefits Tool (Gastric Sleeve)
Bariatric Surgery Health Benefits Tool
Bariatric surgery “cures” or significantly improves many obesity-related health conditions, including:
- Diabetes
- Sleep apnea
- Hypertension
- Joint issues
- … and many others
Select your health conditions in the tool, then click the Submit button to find out the impact a procedure like gastric sleeve can have.
Click here to learn moreAlso see...

References for How to Calculate BMI
- U.S. Department of Health and Human Services. Obesity in Adults. Available at: http://www.ahrq.gov/research/obesity2.htm. Accessed: August
30, 2009. - Mary Anne McCaffree, MD, Chair. The clinical utility of measuring body mass index and waist circumference in the diagnosis and management of adult overweight and obesity. June 2008. Available at: http://www.ama-assn.org/ama1/pub/upload/mm/
38/a08csaphreports.pdf. Accessed: August 15, 2009. - National Heart Lung and Blood Institute – Obesity Education Initiative. Information for Patients and the Public. Available at: http://www.nhlbi.nih.gov/health/public/
heart/obesity/lose_wt/risk.htm. Accessed: September 2, 2009. - Centers for Disease Control and Prevention. Defining Childhood Overweight and Obesity. Available at: http://www.cdc.gov/obesity/childhood/defining.php. Accessed: September 2, 2009.
- Stigler, Stephen M. “Adolphe Quetelet.” Encyclopedia of Statistical Sciences. New York: John Wiley & Sons. 1986.
- Rosen G, Mattison B. Am J Public Health Nations Health. 1969 July; 59(7): 1083–1085.
- Outcomes of bariatric surgery in patients with BMI less than 35 kg/m2. Patricio Fajnwaks, Alexander Ramirez, Pedro Martinez, Enrique Arias, Samuel Szomstein, Raul Rosenthal. Surgery for Obesity and Related Diseases – May 2008 (Vol. 4, Issue 3, Page 329, DOI: 10.1016/j.soard.2008.03.107)
- SFR-117 Safety and efficacy of bariatric surgery in class I obese patients. Melissa Gianos, Abraham Abdemur, Ivan Fendrich, Samuel Szomstein, Raul J. Rosenthal. Surgery for obesity and related diseases : official journal of the American Society for Bariatric Surgery 1 May 2011 (volume 7 issue 3 Page 370 DOI: 10.1016/j.soard.2011.04.172)