How to use
Type your Height in cm and your Weight in kg, and Result shows your BMI with the name of the category it falls in. The calculator takes metric units only, so if you know your height in feet and inches or your weight in pounds, convert them before you type. It accepts heights from 50 to 250 cm and weights from 2 to 400 kg.
Read the result from the top down:
- BMI and category name: your weight in kilograms divided by the square of your height in meters, shown to one decimal place. The category names (for example, Healthy weight) are the ones the CDC itself uses. The copy button next to the number copies a single line such as
BMI 22.9 (Healthy weight). - Category bar: six categories drawn at equal width, with a vertical line marking where your BMI sits. The numbers above the bar are the BMI values where the category changes. The numbers below it are the weights (kg) that give those BMIs at the height you entered. Because every segment is the same width, you cannot judge how wide or narrow a BMI range is from the size of its segment. On a narrow screen the category names and ranges appear as a list under the bar.
- Notes: three lines summarizing how the CDC says these categories should be used.
Adult BMI categories from the WHO and CDC
The World Health Organization (WHO) defines overweight in adults as a BMI of 25 or more and obesity as a BMI of 30 or more. The US Centers for Disease Control and Prevention (CDC) uses the same cutoffs and splits obesity into three classes. The CDC’s categories are meant for adults aged 20 and older.
| Category (name on screen) | BMI | Weight where the category starts at 175 cm |
|---|---|---|
| Underweight | under 18.5 | |
| Healthy weight | 18.5 to under 25 | 56.7 kg |
| Overweight | 25 to under 30 | 76.6 kg |
| Class 1 obesity | 30 to under 35 | 91.9 kg |
| Class 2 obesity | 35 to under 40 | 107.2 kg |
| Class 3 obesity (severe) | 40 and above | 122.5 kg |
The last column is what you see under the bar when you enter a height of 175. At that height, a weight of 70 kg gives 70 ÷ (1.75 × 1.75) = 22.86, so your BMI is 22.9, Healthy weight. At 80 kg it is 26.1, Overweight.
What the CDC says BMI is for
The CDC describes BMI as a quick, low-cost screening measure of how much you weigh relative to your height. In other words, it is not a diagnostic tool. BMI cannot tell fat from muscle or bone, and it says nothing about what kind of fat you have or where on your body it sits.
To judge one person’s health, the CDC advises looking at BMI together with four other things:
- Medical history: conditions you have now and your family history
- Health behaviors: diet, physical activity, sleep
- Physical exam findings: blood pressure, muscle mass
- Lab results: blood sugar, cholesterol
The WHO likewise notes that other measurements, such as waist circumference, can be used alongside BMI to identify overweight and obesity. This calculator only takes height and weight, so it cannot show you any of that.
Obesity around the world in numbers
According to the WHO, 45% of adults aged 18 and older worldwide, about 2.6 billion people, were overweight in 2024. In 1990 the figure was 25%. Of those overweight adults, about 940 million, or roughly 16% of all adults, were living with obesity, and the prevalence of obesity among adults more than doubled between 1990 and 2024.