There’s no single number that works for everyone. Your ideal weight depends on your height, sex, age, muscle mass, and body frame. BMI is the most common starting point, but it’s just one tool, and combining it with a couple of waist measurements gives you a much clearer picture of where you stand.
What BMI Tells You (and What It Doesn’t)
Body mass index divides your weight in kilograms by the square of your height in meters. The World Health Organization classifies results into three broad categories: under 18.5 is underweight, 18.5 to 24.9 is healthy weight, 25 and above is overweight, and 30 and above is obese. For a quick example, a 5’9″ person falls into the healthy range at roughly 125 to 168 pounds.
BMI is useful as a population-level screening tool, but it can’t distinguish between fat and muscle. A study of collegiate athletes found that BMI and body fat percentage agreed on the correct weight category only about 59% of the time. The most common error was BMI labeling athletes “overweight” when their actual body fat was healthy. So if you carry significant muscle, BMI will overestimate your fatness. Conversely, someone with little muscle and a normal BMI may still carry excess fat around their organs.
Your Ethnicity Changes the Thresholds
Standard BMI cutoffs were developed primarily from data on white European populations. Research shows that South Asian and Chinese populations develop diabetes and heart disease at substantially lower BMIs. For South Asian populations, a BMI of 23 to 27.5 indicates increased risk, and anything above 27.5 is high risk, compared to 25 and 30 in white populations. Studies in Chinese adults found overweight cutoffs around 22.5 to 22.8, and obesity cutoffs around 25.9 to 26.6, depending on sex. One Indian study placed the overweight threshold as low as 21.9.
If you’re of South Asian, Chinese, or Southeast Asian descent, the “healthy” BMI range for you is narrower than the standard chart suggests. A BMI of 24 might look fine by general standards but could signal meaningful metabolic risk.
Waist Measurements Matter More Than You Think
Where you carry fat matters as much as how much you carry. Fat stored around your midsection, surrounding your liver, kidneys, and intestines, is the type most strongly linked to heart disease, type 2 diabetes, and metabolic problems. Two people at the same weight can have very different health risks based on their waist size alone.
For women, disease risk starts rising at a waist circumference of 80 cm (about 31.5 inches) and is greatly increased at 88 cm (about 34.5 inches). For men, those thresholds are 94 cm (37 inches) and 102 cm (40 inches). Measure at your belly button level, standing up, after breathing out normally.
The Waist-to-Height Ratio
An even simpler check: keep your waist circumference below half your height. A waist-to-height ratio between 0.4 and 0.5 is generally considered healthy. Between 0.5 and 0.6 suggests increased risk. Above 0.6 signals high risk and a clear need to reduce abdominal fat. If you’re 5’10” (178 cm), that means aiming for a waist at or under 89 cm (35 inches). This single number performs surprisingly well as a health predictor across different ages, sexes, and ethnicities.
Waist-to-Hip Ratio
The WHO defines abdominal obesity as a waist-to-hip ratio above 0.90 for men and above 0.85 for women. To calculate yours, measure your waist at its narrowest point and your hips at their widest, then divide waist by hips. Exceeding those thresholds substantially increases your risk of metabolic complications.
Body Fat Percentage Gives a Clearer Picture
There’s no universally agreed-upon ideal body fat percentage, but a large 2025 study using U.S. national survey data defined “overweight” as 25% body fat or higher for men and 36% or higher for women. “Obesity” was defined as 30% or more for men and 42% or more for women. These numbers are harder to measure at home, though smart scales, skinfold calipers, and DEXA scans can all give you estimates of varying accuracy.
A newer formula called Relative Fat Mass (RFM) estimates your body fat using only your height and waist circumference, and research from Cedars-Sinai found it predicts body fat more accurately than BMI. The formulas are straightforward: for men, it’s 64 minus (20 times height divided by waist circumference). For women, it’s 76 minus (20 times height divided by waist circumference). Use the same units for both measurements. The result is your estimated body fat percentage.
Your Frame Size Shifts the Range
Bone structure varies. A person with a large frame naturally weighs more than someone of the same height with a small frame, even at identical body fat levels. You can estimate your frame size by measuring your wrist circumference.
- Women under 5’2″: small frame if wrist is under 5.5″, medium if 5.5″ to 5.75″, large if over 5.75″
- Women 5’2″ to 5’5″: small under 6″, medium 6″ to 6.25″, large over 6.25″
- Women over 5’5″: small under 6.25″, medium 6.25″ to 6.5″, large over 6.5″
- Men over 5’5″: small 5.5″ to 6.5″, medium 6.5″ to 7.5″, large over 7.5″
If you have a large frame, expect your healthy weight to fall toward the upper end of any BMI-based range. If you have a small frame, the lower end is more realistic. This won’t shift things dramatically, maybe 10 to 15 pounds in either direction, but it helps explain why a single number from a height-weight chart never feels quite right.
Weight and Aging
The relationship between weight and health shifts as you get older. In adults over 65, being slightly overweight by BMI standards is associated with lower mortality than being at the lean end of “normal.” A large study of hospitalized older adults found that mortality was highest in those with very low BMIs (under 16) and decreased steadily as BMI increased, leveling off in the obese range. Men with a BMI under 16 had nearly double the mortality risk of normal-weight men, while those with a BMI of 35 to 39.9 had roughly half the risk.
This doesn’t mean gaining weight in your 70s is protective. What it does mean is that carrying a few extra pounds appears to provide a buffer against illness, falls, and the muscle wasting that accelerates with age. For older adults, maintaining muscle through strength training and adequate protein intake matters more than chasing a lean BMI number.
A Practical Approach to Finding Your Target
Rather than fixating on a single number on the scale, use a combination of measurements to assess where you are. Start with BMI as a rough guide, adjusting the thresholds downward if you’re of South or East Asian descent. Then measure your waist. If your waist-to-height ratio is under 0.5, your waist circumference is below the risk thresholds for your sex, and your BMI is in a reasonable range, you’re in good shape regardless of what the scale says.
If you’re muscular and your BMI reads high, the waist measurements will catch that. A “overweight” BMI paired with a waist-to-height ratio of 0.45 tells a very different story than the same BMI with a ratio of 0.58. The combination of these numbers gives you a far more honest assessment than any single metric, and all you need is a tape measure.