BMI Calculator

Calculate your Body Mass Index and see your weight category.

Height (cm)

Weight (kg)

Results

Your BMI

Category

Body Mass Index (BMI) is a simple weight-to-height ratio used since the 19th century and adopted by the World Health Organization as a population-level screen for weight categories in adults. It is popular because the formula needs only two numbers and produces one easy-to-read value, which makes it cheap to use in clinics, surveys, and fitness apps. For a quick first look at where weight sits relative to height, BMI is still a sensible starting point.

That said, BMI is a screening tool, not a diagnosis. It does not actually measure body fat, muscle, or where fat is carried. A muscular athlete and a sedentary person of the same height and weight will share a BMI but have very different health profiles. Age, sex, ethnicity, and frame size all shift the picture. The WHO itself notes that BMI is most useful when tracked over time and combined with other indicators such as waist circumference, blood pressure, and blood work. Some guidelines suggest that waist-to-hip ratio or waist circumference alone is a better predictor of metabolic risk for some ethnic groups.

For anyone under 18, pregnant, very muscular, or living with a condition that affects body composition, BMI on its own can be misleading. Pediatricians use age- and sex-specific percentiles instead. The result here is best read as a single data point in a broader picture, not as a verdict on health. Trends matter more than single readings: a steady BMI of 23 in a person who lifts is very different from a steady BMI of 23 in a sedentary person, even though the number is identical.

The units of the form are metric by default (centimeters and kilograms), which keeps the math identical to the underlying formula. To convert: 1 inch equals 2.54 cm, 1 foot equals 30.48 cm, and 1 kg equals 2.205 lb. A quick check: an adult 170 cm tall with a BMI of 22 weighs about 63.6 kg, and the same adult with a BMI of 25 sits at 72.3 kg. That small-looking range of about 9 kg spans the entire normal-to-overweight boundary, which is a useful reminder that a few kilos can move the category.

How to use

Enter height in centimeters (for example, 175) and weight in kilograms (for example, 70).
Click calculate to see the BMI number and the matching weight category.
Check the optional normal range for the entered height to see what weight band falls into a healthy BMI.
Repeat the calculation if needed with a target weight to find out the BMI that target would produce.

Formula

BMI = weight (kg) ÷ height (m)². Example: 70 kg divided by (1.75 m × 1.75 m) = 22.9 kg/m².

Interpreting your results

Standard WHO categories for adults: below 18.5 is underweight, 18.5 to 24.9 is normal weight, 25.0 to 29.9 is overweight, and 30.0 or higher is obese (often split into class I 30-34.9, class II 35-39.9, and class III 40+). Being in the normal range is associated with lower average risk for weight-related conditions, but it does not guarantee good health. A high BMI with a small waist and active lifestyle is different from a high BMI with central fat and low activity. Pair the number with waist circumference and how a person actually feels and moves.

Frequently asked questions

What is a healthy BMI?

For most adults, 18.5 to 24.9 is considered the normal range. The 'ideal' point within that band varies by body type, ethnicity, and personal health history, and there is no single number that fits everyone.

Is a BMI of 25 overweight?

By the WHO cutoff, yes: 25.0 to 29.9 is the overweight category. A single value just over 25 is often within normal variation and not a reason for alarm, but it can be a useful prompt to look at trends in weight, diet, and activity.

Can children and teens use this calculator?

No, this calculator is for adults. For children and adolescents up to 19, BMI is interpreted using age- and sex-specific percentiles (CDC or WHO growth charts), which a pediatrician can plot. A separate child BMI tool is the right choice for that age group.

Why does my BMI say overweight but I look slim?

Muscle is denser than fat, so muscular people often land in the overweight or even obese BMI range despite low body fat. Athletes, strength trainers, and people with heavy manual jobs are common examples. In that case, body fat percentage and waist-to-hip ratio are more useful numbers.