The short answer
For adults age 20 and older, CDC calls a BMI of 18.5 to under 25 the healthy weight range. Below 18.5 is underweight. From 25 to under 30 is overweight, and 30 or more is obesity. WHO uses the same 25 and 30 cut points.
For a person who is 175 cm tall, that healthy range works out to about 56.7 kg up to just under 76.6 kg. At 5 feet 8 inches, it's about 121.7 lb up to just under 164.4 lb. That's a spread of over 40 pounds, which tells you the range is wide on purpose.
Why the range is a range
BMI cut points come from population studies. They mark where health risks tend to rise across large groups of people. They were never meant to pick one perfect weight for you.
So a BMI of 19 isn't healthier than 24 just because it's lower, and the middle of the range isn't a target. If your BMI sits anywhere from 18.5 to just under 25, the number itself isn't flagging anything. Other measures will tell you more.
Who the standard range fits poorly
Muscle is the classic exception. BMI only sees weight and height, so a strength athlete can read as overweight with little body fat. The reverse happens too. An older adult who has lost muscle can have a normal BMI while carrying more fat than the number suggests.
Background matters as well. The UK's NICE guideline uses lower thresholds for adults of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background, because health risks start at lower BMIs in these groups. There, overweight starts at 23 and obesity at 27.5.
Children, teens and pregnant people need different tools entirely. For ages 2 through 19, CDC uses BMI-for-age percentiles on growth charts, because body fat changes as kids grow and differs between boys and girls. During pregnancy, weight gain is expected, so adult categories can't read it.
What to check alongside BMI
Waist size is the easiest add-on. Fat around the middle is linked to heart and metabolic risk, and BMI can't see it. NICE suggests dividing your waist by your height. Under 0.5 is the usual goal, and 0.5 to 0.59 is a reason to pay closer attention.
Beyond that, a clinician will look at blood pressure, blood sugar and cholesterol, your family history, your activity level and how your weight has changed over time. Those tell far more about your health than BMI does.
- Waist-to-height ratio (waist / height)
- Blood pressure
- Blood sugar and cholesterol from a routine blood test
- Recent weight changes you can't explain
How to use your number
Work out your BMI with our BMI calculator, which also shows where each category starts at your height. Use a measured height and weight rather than a guess, since a small error matters most near a boundary. If you're in the healthy range, there's nothing to chase. If you're outside it, treat the number as a reason to have a conversation with a doctor, not as a verdict.
Measure the same way each time if you track it: same scale, light clothes, morning. Normal day-to-day swings can flip the category if you're near a boundary.
Frequently asked questions
Is a BMI of 25 bad?
Not on its own. 25 is where CDC's overweight category starts, but BMI is a screening number. Waist size, blood tests and blood pressure tell you much more about risk at that level.
Is a BMI of 18 too low?
It's below the 18.5 cutoff, so CDC calls it underweight. Some people are naturally lean, but unexplained weight loss or a low BMI with symptoms is worth raising with a doctor.
Does a healthy BMI change with age?
Not on the CDC adult table, which uses the same range for everyone 20 and older. Muscle loss with age can make BMI less telling for older adults, though.
What BMI do Asian adults use?
NICE in the UK uses 23 for overweight and 27.5 for obesity for adults of South Asian, Chinese and other Asian backgrounds, among others. CDC's U.S. table uses the standard cut points for everyone.
References
These sources support the method or guidance used for BMI Calculator. Verify time-sensitive rules at the source.
Try the calculator
Open BMI Calculator, enter your scenario, and compare its supporting rows with this guide's method and checks.