BMI Calculator
Find out if your weight is in a healthy range for your height, in just a few seconds.
BMI ranges for adults.
Underweight
< 18.5
Healthy weight
18.5 – 24.9
Overweight
25.0 – 29.9
Obesity (Class I)
30.0 – 34.9
Obesity (Class II)
35.0 – 39.9
Obesity (Class III)
≥ 40.0
Children & teens (ages 2–19)
BMI for kids is measured differently. Doctors compare it to growth charts by age and sex, called percentiles. Under the 5th percentile is underweight. The 5th to 85th is healthy. The 85th to 95th is overweight. Above the 95th is obesity. This calculator shows adult ranges only, so please use paediatric charts for children.
What do these words mean?
Body Mass Index (BMI)
A number that gives you a rough idea of whether your weight is healthy for your height. It doesn't measure body fat directly, but it's quick and easy to calculate and widely used as a first check.
You weigh 70 kg and are 1.75 m tall. BMI = 70 ÷ (1.75 × 1.75) ≈ 22.9. That falls in the healthy weight range.
Weight
How heavy you are. You can enter it in kilograms (kg) or pounds (lb). We convert automatically, so just use whichever unit your scale shows.
70 kg is about 154 lb. If your scale shows pounds, switch to imperial mode and type that number in.
Height
How tall you are. You can enter it in centimetres (cm) or in feet and inches. Both work fine here.
175 cm is the same as 1.75 m, or about 5 feet 9 inches. If you only know one of those formats, just enter that one.
BMI Categories
Labels that tell you what a BMI number means for adults. They come from the World Health Organization (WHO) and the CDC and apply to people aged 20 and older.
BMI 17 = Underweight. BMI 22 = Healthy weight. BMI 27 = Overweight. BMI 32 = Obesity.
Common Questions.
BMI stands for Body Mass Index. It's a number that tells you if your weight is healthy for your height.
A higher BMI usually means more body fat. But it's just one piece of the picture. Doctors use it as a starting point, not the whole answer.
You divide your weight by your height squared. Here's how it looks:
Metric: BMI = weight (kg) ÷ [height (m)]²
So someone who's 70 kg and 1.75 m tall: 70 ÷ (1.75 × 1.75) ≈ 22.9
Imperial: BMI = (weight (lb) ÷ [height (in)]²) × 703
Our calculator handles all of this for you. Just enter your numbers and you're done.
Whichever ones you know. You can use kg and cm, or pounds and feet/inches. Just pick the one your scale uses.
We convert everything automatically in the background.
Here's a simple breakdown:
Below 18.5 — Underweight
18.5 to 24.9 — Healthy weight
25 to 29.9 — Overweight
30 or above — Obesity
For example: BMI 22 is healthy. BMI 27 is overweight. BMI 32 falls in the obesity range.
Not always. BMI works well for most adults, but it doesn't measure body fat directly.
Someone very muscular, like an athlete, can have a high BMI without any health problem. That's because muscle weighs more than fat.
If you're not sure what your number means for you, a doctor is the right person to ask.
BMI works differently for kids and teens aged 2 to 19.
Instead of fixed ranges, doctors use growth charts that take age and sex into account. These are called percentiles.
The adult numbers in this calculator don't apply to children. Please don't use them that way.
BMI is less useful in those cases.
Pregnancy adds weight that has nothing to do with body fat. Athletes often carry a lot of muscle, which can push the BMI number up even when they're perfectly healthy.
In both situations, a doctor can give a much better read.
A BMI that's very high or very low can point to a health risk worth looking into. It's a quick first check, nothing more.
Doctors usually look at BMI alongside other things like blood pressure, waist size, and how active you are day to day.
We show your BMI to one decimal place, which is the standard used in medical settings.
The full calculation runs at high precision in your browser, then rounds for display. So 22.849 shows as 22.8, for example.
Yes, 100% free. And everything runs right in your browser.
We don't save, share, or track anything you type. Your height and weight are used only to show you the result. They never leave your device.