The most common way to check if you’re overweight is by calculating your body mass index, or BMI. A BMI between 25 and 29.9 falls in the overweight range for most adults. But BMI is just one piece of the picture, and it misclassifies a surprisingly large number of people. Combining it with a couple of other simple measurements gives you a much more reliable answer.
How to Calculate Your BMI
BMI uses a simple formula: divide your weight in kilograms by your height in meters squared. If you prefer pounds and inches, multiply your weight in pounds by 703, then divide by your height in inches squared. Most people skip the math and use a free online calculator from the CDC or NHS.
The CDC defines the categories for adults 20 and older like this:
- Underweight: below 18.5
- Healthy weight: 18.5 to 24.9
- Overweight: 25 to 29.9
- Class 1 obesity: 30 to 34.9
- Class 2 obesity: 35 to 39.9
- Class 3 (severe) obesity: 40 or higher
These ranges were designed around population-level data and work reasonably well as a starting point. If your number lands at 25 or above, it’s worth looking at the other measurements below before drawing conclusions.
Why BMI Gets It Wrong for Many People
BMI treats all weight the same. It can’t tell the difference between muscle, bone, and fat. A muscular person with low body fat can easily land in the “overweight” category despite being in excellent health. This is especially common in athletes and people who strength train regularly.
The error rate is not small. When researchers compared BMI classifications against DEXA scans, which measure actual body composition using low-dose X-rays, BMI misclassified roughly 40% of participants. Even more striking, a BMI of 30 or higher correctly identified excess body fat only about half the time, meaning the other half of people carrying too much fat were missed entirely. BMI can both overestimate and underestimate the problem depending on your body type.
Measure Your Waist
Your waist circumference is one of the simplest and most useful numbers you can track at home. Fat stored around your midsection, sometimes called visceral fat, wraps around internal organs and is more strongly linked to heart disease and type 2 diabetes than fat stored in your hips or thighs.
To measure, wrap a tape measure around your bare waist at the level of your belly button, standing up straight and breathing normally. Don’t suck in your stomach. According to Harvard Health, the thresholds that signal higher health risk are 35 inches or more for women and 40 inches or more for men.
A person with a “normal” BMI but a large waist measurement can still face elevated metabolic risk. The reverse is also true: someone whose BMI says “overweight” but who carries weight in their legs and hips rather than their midsection may be at lower risk than the number suggests.
The Waist-to-Height Ratio
An even simpler rule of thumb comes from the NHS: your waist should measure less than half your height. So if you’re 5 feet 8 inches tall (68 inches), your waist should stay under 34 inches. This ratio adjusts automatically for body size, which makes it useful across different heights and builds. It also tends to predict cardiovascular risk better than BMI alone.
Body Fat Percentage
If you want the most direct answer to whether you’re carrying excess fat, body fat percentage is what you’re really asking about. A 2025 study using US national survey data defined overweight as a body fat percentage of 25% or higher for men and 36% or higher for women. Obesity thresholds were 30% for men and 42% for women.
Getting an accurate body fat reading at home is tricky. Bathroom scales with bioelectrical impedance sensors give rough estimates but can swing by several percentage points depending on your hydration. The most accurate options, like DEXA scans or air displacement pods, are available through clinics and some gyms for a fee. They’re worth considering if your BMI puts you on a borderline and you want a clearer picture.
Different Thresholds for Different Populations
The standard BMI cutoffs were developed primarily from data on white European populations. For people of Asian descent, health risks like type 2 diabetes and heart disease start climbing at lower BMI levels. The World Health Organization proposed adjusted thresholds for Asian populations: overweight begins at a BMI of 23 rather than 25, and obesity at 25 rather than 30. A substantial proportion of Asian individuals develop metabolic problems well below the standard cutoff of 25, so using the general categories can give a false sense of security.
How It Works for Children and Teens
BMI categories for children and teens between ages 2 and 19 work differently than for adults. Because kids are still growing, their BMI is compared against growth charts for their age and sex, producing a percentile ranking rather than a fixed number. A child at or above the 85th percentile but below the 95th is considered overweight. At the 95th percentile or above, the classification is obesity. Your child’s pediatrician calculates this at routine checkups, and the CDC offers an online calculator if you want to check between visits.
Physical Signs Worth Noticing
Beyond the numbers, your body sometimes offers its own signals. Persistent joint pain in weight-bearing areas like knees and lower back, getting winded during activities that used to feel easy, and snoring that disrupts your sleep can all point toward carrying extra weight. One lesser-known sign is darkened, velvety patches of skin in the armpits or along the back and sides of the neck, a condition called acanthosis nigricans. This skin change is linked to elevated blood sugar and insulin resistance, which often accompany excess body fat.
Clothes fitting differently over time, especially around the midsection, is another practical indicator that many people notice before they ever step on a scale.
Putting It All Together
No single measurement tells the full story. The most reliable approach is to check several: calculate your BMI, measure your waist, and compare your waist to your height. If two or three of those numbers land in concerning ranges, there’s a strong signal that your weight is affecting your health. If only your BMI is elevated but your waist measurement and overall fitness are solid, the picture is more nuanced.
Body fat percentage testing adds another layer of clarity if you want it, especially if you’re muscular or your BMI sits right on a borderline. And if you’re of Asian descent, use the lower BMI thresholds rather than the standard ones. The goal isn’t to fixate on any single number but to get a realistic sense of where you stand so you can make informed choices about what, if anything, to change.