There’s no single number that represents your ideal weight. A healthy weight depends on your height, age, sex, muscle mass, and where your body stores fat. BMI is the most common starting point: for adults, a “healthy weight” BMI falls between 18.5 and 24.9. But that number alone misses important context, and newer measures do a better job of capturing what actually matters for your health.
What BMI Tells You (and What It Doesn’t)
BMI divides your weight in kilograms by your height in meters squared. The CDC uses these categories for adults 20 and older:
- Underweight: below 18.5
- Healthy weight: 18.5 to 24.9
- Overweight: 25 to 29.9
- Obesity: 30 or higher
So a person who is 5’6″ would fall in the healthy range at roughly 115 to 154 pounds. At 5’10”, that range is about 132 to 174 pounds. You can plug your own height into any online BMI calculator to get your range in seconds.
The problem is that BMI was designed as a population-level screening tool, not a personal health verdict. The American Medical Association adopted a policy recognizing its significant limitations: it was originally developed using data from non-Hispanic white populations, it doesn’t distinguish fat from muscle, and it loses predictive accuracy when applied to individuals rather than large groups. The AMA now recommends using BMI alongside other measures like waist circumference, body composition, and metabolic markers rather than relying on it alone.
Why Waist Size May Matter More
Where you carry fat is at least as important as how much you weigh. Fat stored deep around your organs (visceral fat) drives far more health risk than fat stored under the skin on your hips or thighs. Your waist measurement captures this in a way the bathroom scale cannot.
The simplest approach is the waist-to-height ratio. Divide your waist circumference by your height, both in the same units. If the result is above 0.5, your risk of cardiovascular disease rises, even if your BMI looks normal. Research from the University of Pittsburgh found that people with a BMI under 30 but a waist-to-height ratio over 0.5 showed higher rates of coronary artery calcification, a key marker of heart disease, even without other risk factors. In practical terms: your waist should measure less than half your height.
To measure accurately, wrap a tape measure around your bare waist at the level of your navel, standing relaxed without sucking in. That single number, compared to your height, tells you more about metabolic risk than your weight on a scale.
Body Fat Percentage by Age and Sex
Two people can weigh the same and look completely different because muscle is denser than fat. Body fat percentage gets closer to what’s actually going on inside your body. National data from DXA scans (the gold standard for body composition) of over 22,000 Americans shows how body fat naturally varies:
For men, average body fat ranges from about 23% in the late teens to 31% by ages 60 to 79. For women, the range runs from about 32% in childhood to 42% by that same older age bracket. Women carry more body fat at every age, which is normal and reflects biological differences in hormone levels and reproductive function.
Generally, fitness organizations consider body fat in the range of 10 to 20% healthy for men and 18 to 28% healthy for women of reproductive age. These aren’t hard cutoffs, and healthy ranges shift upward as you get older. What matters more than hitting a specific number is the trend over time: a steady increase in body fat, particularly around the midsection, signals rising risk even if your weight stays stable.
A Better Formula: Relative Fat Mass
If you want a body fat estimate without expensive scans, Relative Fat Mass (RFM) is a newer formula that outperforms BMI. Researchers at Cedars-Sinai developed it after finding that BMI misclassifies about 60% of women and 13% of men when determining obesity. RFM requires only a tape measure and your height:
- Men: 64 minus (20 × height ÷ waist circumference)
- Women: 76 minus (20 × height ÷ waist circumference)
Use the same units for both height and waist. The result estimates your body fat percentage. It’s not perfect, but it captures the fat-versus-muscle distinction that BMI ignores entirely, and you can track it at home over time.
Your Ideal Weight Changes With Age
The “healthy” BMI range of 18.5 to 24.9 was set for the general adult population, but it doesn’t fit older adults well. A large meta-analysis found that for people over 65, being in the overweight BMI range (25 to 29.9) carried no increased mortality risk. In fact, being at the lower end of the so-called healthy range was more dangerous: a BMI of 21 to 21.9 carried a 12% higher mortality risk than a BMI of 23 to 23.9, and a BMI of 20 to 20.9 carried a 19% higher risk.
This “obesity paradox” in older adults likely reflects the protective role of muscle and bone mass. As you age, you naturally lose muscle (a process called sarcopenia), and carrying slightly more weight can buffer against frailty, falls, and the wasting that accompanies serious illness. For adults over 65, a BMI in the 23 to 30 range is generally associated with the lowest risk. Losing weight unintentionally in later life is a red flag worth investigating, not a welcome surprise.
When the Scale Lies: Athletes and Muscle Mass
If you strength train seriously or play competitive sports, BMI will likely overestimate your body fat. A study of over 200 college athletes found that 38 had a BMI of 25 or higher, technically classifying them as overweight or obese. But when researchers measured their actual body fat using skinfold thickness, only four of those 38 had excess fat. The other 27 had high muscle mass that inflated their BMI.
Among the female athletes classified as overweight by BMI, only 20% actually had elevated body fat. For men, it was just 4%. If you carry significant muscle, your weight will be higher than BMI charts suggest it should be. In that case, waist-to-height ratio, body fat percentage, or RFM will give you a far more accurate picture of your health than the scale.
How to Find Your Own Target
Rather than fixating on a single goal weight, use a combination of measures to build a fuller picture. Start with BMI for a rough range, then check your waist-to-height ratio. If it’s under 0.5, that’s a strong sign your weight is in a healthy place regardless of what the scale says. If you want more detail, calculate your RFM or get a body composition test through a gym or clinic.
Pay attention to metabolic health markers at your regular checkups: blood pressure, blood sugar, and cholesterol. There is no universal agreement on what makes someone “metabolically healthy” at any given weight, but normal results on those three measures are a solid indication that your body is functioning well. Some people at a higher weight have perfectly clean metabolic profiles, and some people at a normal weight do not.
Your healthiest weight is one you can maintain without extreme restriction, where you sleep well, move comfortably, and your bloodwork looks good. The number on the scale is one data point in a much larger picture.