BMI and body measures
BMI is a screening number, and it misses a lot. This tool adds your waist-to-height ratio and the weight range for your height, using published cutoffs, and says what each number can and cannot tell you.
Your result will appear here.
Limits. These are adult measures. They are not meant for children and teens or for pregnancy. BMI does not measure body fat and can mislead in very muscular adults and in older adults. None of this decides whether a medicine is right for you. That is a conversation with a licensed clinician who knows your history.
What BMI can and cannot tell you
The CDC calls BMI a screening measure and says it should be considered with other factors when looking at one person's health. A 2025 commission of 58 experts, published in The Lancet Diabetes and Endocrinology, went further: it recommended using BMI as a population and screening tool, not as an individual measure of health. It says excess body fat should be confirmed with a direct fat measurement or at least one other body measure, such as waist circumference, waist-to-hip ratio or waist-to-height ratio. For a BMI over 40, it says excess body fat can be assumed.
The commission also splits obesity into preclinical obesity (excess body fat with organs and tissues still working normally) and clinical obesity (excess body fat that is already affecting how organs, tissues or daily activities work). That difference is why one BMI number cannot say how much a person's health is affected.
BMI bands
| Band | Standard (CDC, NICE) | Adjusted (NICE, some family backgrounds) |
|---|---|---|
| Underweight | Below 18.5 | Below 18.5 |
| Healthy weight | 18.5 to 24.9 | 18.5 to 22.9 |
| Overweight | 25.0 to 29.9 | 23.0 to 27.4 |
| Obesity, class 1 | 30.0 to 34.9 | 27.5 to 32.4 |
| Obesity, class 2 | 35.0 to 39.9 | 32.5 to 37.4 |
| Obesity, class 3 | 40.0 or higher | 37.5 or higher |
NICE says people from these backgrounds are prone to central fat and can face cardiometabolic risk at a lower BMI. The CDC applies one set of cutoffs to every adult. NICE says BMI should be read with caution in adults with a lot of muscle and in people 65 and older. The class 2 and 3 adjusted values follow NICE's rule of lowering the standard cutoffs by 2.5.
Waist-to-height ratio
Your waist divided by your height, in the same unit. NICE uses it for adults with a BMI under 35, for all sexes and ethnic backgrounds, including people with a lot of muscle. A review of studies covering more than 300,000 adults found that waist-to-height ratio did a better job than BMI at flagging risk factors for heart and metabolic disease.
| Waist-to-height ratio | What NICE calls it |
|---|---|
| 0.4 to 0.49 | Healthy central fat |
| 0.5 to 0.59 | Increased central fat, increased health risk |
| 0.6 or more | High central fat, further increased health risk |
NICE also gives a simple rule: keep your waist under half your height, a ratio under 0.5.
Where the trials drew the line
The large trials of semaglutide and tirzepatide enrolled adults with a BMI of 30 or higher, or 27 or higher with at least one weight-related condition, for example high blood pressure, abnormal cholesterol or sleep apnea. Those trials used the standard BMI numbers. The result box above shows where your BMI falls against that line. It is context for reading trial results, not a test for who should take a medicine.
Read more in the beginner guide on what BMI can and cannot tell you, then see what the trials found in the trial results explorer.
Sources
- Adult BMI categories U.S. Centers for Disease Control and Prevention. Page dated March 19, 2024. Regulator
- Overweight and obesity management (NICE guideline NG246): Identifying and assessing overweight, obesity and central adiposity National Institute for Health and Care Excellence (England). Adult BMI categories, adjusted BMI thresholds for some ethnic backgrounds, and waist-to-height ratio bands. Regulator
- Definition and diagnostic criteria of clinical obesity Rubino F, et al. Lancet Diabetes Endocrinol. 2025;13(3):221-262. PMID 39824205. Funding: Not stated in the abstract. Journal article
- Waist-to-height ratio is a better screening tool than waist circumference and BMI for adult cardiometabolic risk factors: systematic review and meta-analysis Ashwell M, Gunn P, Gibson S. Obes Rev. 2012;13(3):275-286. PMID 22106927. Funding: Not stated in the abstract. Journal article
- Once-weekly semaglutide in adults with overweight or obesity (STEP 1) Wilding JPH, et al. N Engl J Med. 2021;384(11):989-1002. PMID 33567185. Funding: Novo Nordisk. Journal article
- Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1) Jastreboff AM, et al. N Engl J Med. 2022;387(3):205-216. PMID 35658024. Funding: Eli Lilly. Journal article