There’s no single number that works for everyone. Your ideal weight depends on your height, sex, age, muscle mass, and body frame. BMI gives you a starting range, but it’s only one piece of the picture. A combination of BMI, waist measurement, and body composition paints a much more accurate portrait of whether your weight is healthy.
The BMI Starting Point
Body mass index, or BMI, is calculated by dividing your weight in kilograms by your height in meters squared. The CDC defines a healthy BMI as 18.5 to 24.9 for adults 20 and older. Below 18.5 is underweight. A BMI of 25 to 29.9 is overweight, and 30 or above falls into the obesity range, which is further divided into three classes (30 to 34.9, 35 to 39.9, and 40 or higher).
In practical terms, for someone who is 5’6″, a healthy BMI translates to roughly 115 to 154 pounds. For someone 5’10”, it’s about 129 to 174 pounds. You can calculate your own range by plugging your height into any online BMI calculator, but those raw numbers come with important caveats.
Why BMI Can Be Misleading
BMI cannot distinguish between muscle and fat. It overestimates body fat in people with high muscle mass and underestimates it in people who carry little muscle, particularly older adults and those with chronic illness. A bodybuilder with 6% body fat can register a BMI over 30, placing them in the “obese” category on paper. Meanwhile, someone with a normal BMI could carry a significant amount of internal fat around their organs and appear healthy by this single measure.
BMI also ignores where your fat is distributed. Carrying fat around the midsection (an apple-shaped pattern) poses far greater health risks than carrying it in the hips and thighs. Conditions like type 2 diabetes, heart disease, and insulin resistance are strongly tied to this abdominal fat pattern, and BMI won’t flag it.
Your Waist May Matter More Than Your Weight
A simple measurement that adds real information is the waist-to-height ratio. The guideline is straightforward: keep your waist circumference below half your height. If you’re 5’8″ (68 inches), your waist should stay under 34 inches. A large study in PLOS One found that years of life lost increased dramatically once this ratio exceeded 0.52 for both men and women.
Researchers have proposed three practical zones. A waist-to-height ratio between 0.4 and 0.5 carries minimal increased mortality risk. Between 0.5 and 0.6, you’re in the “consider action” range. Above 0.6, the data shows markedly higher mortality, making it a clear signal to prioritize changes.
To measure your waist accurately, stand up and find the top of your hip bone on your right side. Place a measuring tape horizontally around your abdomen at that level, keeping it parallel to the floor. The tape should be snug but not compressing your skin. Read the measurement at the end of a normal breath out.
Visceral Fat Is the Real Concern
Not all body fat carries the same risk. Subcutaneous fat, the kind you can pinch under your skin, is relatively benign. Visceral fat, which surrounds your internal organs deep in the abdomen, is metabolically active and drives inflammation, insulin resistance, and arterial plaque buildup. Data from the Multi-Ethnic Study of Atherosclerosis found that higher visceral fat was linked to greater heart disease markers across every BMI category, including in people whose weight was technically “normal.”
Here’s what’s striking: when researchers tracked changes over time, increases in visceral fat independently raised the risk of developing metabolic syndrome, while changes in subcutaneous fat had no significant effect. This means two people at the same weight can have very different health outlooks depending on where their fat sits. Your waist measurement is the best home proxy for visceral fat.
Adjustments for Age
The standard healthy BMI range of 18.5 to 24.9 was designed for the general adult population, but it doesn’t fit everyone equally well. For adults over 65, carrying a bit more weight appears protective. Research examining older adult populations found that BMIs below 25 were actually associated with more negative health outcomes, not fewer. The optimal range shifted upward, to roughly 27 to 28 for older men and 31 to 32 for older women, with the worst outcomes appearing below 25 and above 35.
This likely reflects the fact that as people age, maintaining muscle mass and having metabolic reserves becomes critical for surviving illness, surgery, and falls. If you’re over 65 and your BMI sits in the mid-to-upper 20s, that’s generally a good sign, not a reason to diet aggressively.
Adjustments for Ethnicity
Standard BMI thresholds were developed primarily from data on European-descent populations. For people of Asian descent, health risks from excess weight begin at lower BMI values. The Asia-Pacific guidelines classify a BMI of 23 to 24.9 as overweight (compared to 25 in the standard system) and 25 or above as obese (compared to 30). The normal range narrows to 18.5 to 22.9. If you’re of South Asian, East Asian, or Southeast Asian heritage, these lower thresholds give you a more accurate picture of your metabolic risk.
Your Body Frame Changes the Range
Bone structure genuinely affects what you should weigh. A quick way to estimate your frame size is by measuring your wrist circumference. For women between 5’2″ and 5’5″, a wrist under 6 inches indicates a small frame, 6 to 6.25 inches is medium, and over 6.25 inches is large. For men over 5’5″, small frames measure 5.5 to 6.5 inches, medium frames 6.5 to 7.5 inches, and large frames over 7.5 inches.
A large-framed person will naturally and healthily weigh more than a small-framed person of the same height. If your wrist measurement puts you in the large-frame category, aiming for the lower end of a BMI range would be unrealistic and unnecessary. The upper portion of the healthy range is where you’d expect to land.
Body Fat Percentage Fills in the Gaps
If you want the most complete picture, body fat percentage tells you what BMI can’t: how much of your weight is actually fat versus muscle, bone, and water. The World Health Organization recommends men ages 40 to 59 aim for 11% to 21% body fat, with the range shifting to 13% to 24% for men ages 60 to 79. Women naturally carry more essential fat and have correspondingly higher healthy ranges, typically 21% to 35% depending on age.
You can estimate body fat through methods like skinfold calipers (available at most gyms), bioelectrical impedance scales (common consumer scales that send a mild current through your body), or a DEXA scan for the most precise reading. None of these are perfect, but tracking trends over time with the same method gives useful data. If your body fat percentage is in a healthy range, your weight is likely fine regardless of what BMI says.
Putting It All Together
Rather than fixating on a single number on the scale, use multiple checkpoints. Start with BMI to get a ballpark range for your height. Then measure your waist and divide by your height. If that ratio is under 0.5, your abdominal fat is in a low-risk zone. Factor in your age (over 65, a higher BMI is protective), your ethnicity (lower thresholds for Asian populations), and your frame size (larger frames naturally weigh more). If you can, get a body fat percentage reading to see whether your weight is coming from muscle or fat.
Two people who are both 5’7″ and 160 pounds can have completely different health profiles. One might carry significant visceral fat with elevated blood pressure and blood sugar. The other might be muscular with a trim waist and excellent metabolic markers. The number on the scale is just one data point. The measurements around it are what tell the real story.