BMI Calculator

1. 01Enter your weightYour current weight in kilograms.
2. 02Enter your heightYour height in centimeters.
3. 03Read the resultYour BMI and category appear instantly, with an explanation of the classification used.

• 70 kg, 175 cmBMI = 70 ÷ (1.75 × 1.75) = 22.9 → normal weight.
• 95 kg, 175 cmBMI = 95 ÷ (1.75 × 1.75) = 31.0 → obese class 1, since it is at or above 30.
• 50 kg, 175 cmBMI = 50 ÷ (1.75 × 1.75) = 16.3 → underweight, since it is below 18.5.

• BMI does not measure body fat directlyBMI only compares weight to height, without distinguishing muscle from fat. Athletes or people with a lot of muscle mass can have a high BMI despite low body fat.
• Not valid for children or pregnant womenChildren's BMI is calculated using age- and sex-specific growth charts, not the adult formula. Pregnant women have their own weight-gain guidelines, separate from standard BMI categories. This calculator applies only to adults 18 and over.
• Classification standards varyIf a doctor or app shows a different BMI category than this calculator, they may be using a regional guideline or risk-screening framework with lower BMI cutoffs rather than the WHO global classification used here. Some Asian population guidelines, for example, use lower action points, since research indicates cardiometabolic risk can appear at lower BMI levels in some Asian populations. This calculator uses the WHO global classification as its default.

BMI = weight (kg) ÷ [height (m)]². Height in centimeters is divided by 100 first to get a value in meters. This formula is the same worldwide; what differs between countries and institutions is where the category cutoffs fall.

This calculator uses the WHO (World Health Organization) global adult BMI classification: underweight below 18.5; normal weight 18.5 to 24.9; overweight 25 to 29.9; obese class 1 30 to 34.9; obese class 2 35 to 39.9; and obese class 3 at 40 and above.

Some regional guidelines and clinical risk-screening frameworks use lower BMI action points for certain populations — for example, some guidelines for Asian populations use a lower threshold for the 'normal' and 'overweight' categories, reflecting research suggesting cardiometabolic risk (such as diabetes and heart disease) can appear at a lower BMI in some Asian populations than the global thresholds alone would suggest. This calculator uses the WHO global adult classification as its explicit default; if a clinician has given you a different threshold, it likely reflects one of these population-specific guidelines rather than an error in either number.

BMI is a screening tool, not a diagnosis. It does not distinguish muscle mass from body fat, does not account for fat distribution (abdominal fat versus fat elsewhere), and only applies to adults 18 and over — not children or pregnant women. For an accurate assessment of your health, consult a doctor or dietitian who can weigh in other factors like waist circumference, body composition, and medical history.

How do I calculate BMI?

BMI = weight (kg) divided by height in meters, squared. For example, at 70 kg and 175 cm (1.75 m): BMI = 70 ÷ (1.75 × 1.75) = 22.9.

What is a normal BMI?

Under the WHO global classification this calculator uses (its default), normal BMI falls between 18.5 and 24.9. Some regional guidelines for certain populations use a lower threshold, reflecting research on population-specific cardiometabolic risk — ask a healthcare provider which reference range is most relevant to you.

Why does my BMI category differ from another app or my doctor's office?

They may be using a population-specific risk-screening guideline with a lower BMI threshold, rather than the WHO global classification this calculator uses by default. Some guidelines for Asian populations, for example, use lower action points because research suggests cardiometabolic risk can appear at a lower BMI in some Asian populations. This reflects a difference in guidelines, not necessarily an error.

Does BMI apply to children?

No. Children's BMI is calculated using age- and sex-specific growth charts (percentile curves), not the adult formula and categories used here. This calculator is for ages 18 and over only.

Is BMI accurate for athletes or bodybuilders?

Less so. BMI does not distinguish muscle mass from fat, so someone with a lot of muscle can be categorized as "overweight" despite having a low body fat percentage.

Is my data saved?

No. Everything is calculated in your browser; nothing is sent to a server.