BMI (Body Mass Index) is a numerical value calculated from your height and weight. It is used as a screening tool to categorize weight status — underweight, normal, overweight, or obese. It was developed by Adolphe Quetelet in the 1830s.

What is a healthy BMI?

According to the World Health Organization (WHO), a healthy BMI for adults is between 18.5 and 24.9. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese.

BMI is a useful screening tool but has limitations. It does not directly measure body fat and can misclassify muscular individuals as overweight. It also does not account for age, sex, ethnicity, or fat distribution. Use it as a starting point, not a definitive health measure.

What is the BMI formula?

In metric units: BMI = weight in kg ÷ (height in meters)². In imperial units: BMI = 703 × weight in pounds ÷ (height in inches)². For example, a person weighing 70kg at 1.75m has a BMI of 70 ÷ (1.75)² = 22.9.

BMI prime is your BMI divided by 25 (the upper limit of normal weight). A BMI prime of 1.0 means you are exactly at the top of the healthy range. Values below 1.0 are in or below normal; above 1.0 is overweight.

Is BMI the same for men and women?

The calculation is the same, but body fat percentage at the same BMI differs between men and women. Women typically have higher body fat than men at the same BMI. Some researchers argue for gender-specific BMI thresholds.

What BMI is considered obese?

A BMI of 30 or above is classified as obese by the WHO. Obesity is further divided into Class I (30–34.9), Class II (35–39.9), and Class III or severe obesity (40 and above).

Free BMI Calculator Online

Calculate your Body Mass Index in metric or imperial units, see your WHO weight category on a colour gauge, and find the healthy weight range for your height.

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Height (cm)

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Your BMI

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Healthy weight: —
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Medical Disclaimer: The BMI Calculator is for informational purposes only and does not constitute medical advice. Results are estimates based on population averages and may not reflect your individual health status. Consult a qualified healthcare professional before making decisions about your health, diet, or exercise routine.

WHO BMI classification

BMI range	Category	Health risk
Below 18.5	Underweight	May indicate malnutrition or other health issues
18.5 – 24.9	Normal weight	Associated with the lowest health risk
25.0 – 29.9	Overweight	Increased risk of cardiovascular disease
30.0 – 34.9	Obese Class I	Moderate risk
35.0 – 39.9	Obese Class II	Severe risk
40.0 and above	Obese Class III	Very severe (morbid) risk

BMI interpretation differs for children aged 2–19. Children’s BMI uses age- and sex-specific percentiles. Consult a pediatrician for children’s weight assessment.

Frequently Asked Questions

What is BMI?: BMI (Body Mass Index) is a numerical value calculated from your height and weight. It is used as a screening tool to categorize weight status — underweight, normal, overweight, or obese. It was developed by Adolphe Quetelet in the 1830s.
What is a healthy BMI?: According to the World Health Organization (WHO), a healthy BMI for adults is between 18.5 and 24.9. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese.
Is BMI accurate?: BMI is a useful screening tool but has limitations. It does not directly measure body fat and can misclassify muscular individuals as overweight. It also does not account for age, sex, ethnicity, or fat distribution. Use it as a starting point, not a definitive health measure.
What is the BMI formula?: In metric units: BMI = weight in kg ÷ (height in meters)². In imperial units: BMI = 703 × weight in pounds ÷ (height in inches)². For example, a person weighing 70kg at 1.75m has a BMI of 70 ÷ (1.75)² = 22.9.
What is BMI prime?: BMI prime is your BMI divided by 25 (the upper limit of normal weight). A BMI prime of 1.0 means you are exactly at the top of the healthy range. Values below 1.0 are in or below normal; above 1.0 is overweight.
Is BMI the same for men and women?: The calculation is the same, but body fat percentage at the same BMI differs between men and women. Women typically have higher body fat than men at the same BMI. Some researchers argue for gender-specific BMI thresholds.
What BMI is considered obese?: A BMI of 30 or above is classified as obese by the WHO. Obesity is further divided into Class I (30–34.9), Class II (35–39.9), and Class III or severe obesity (40 and above).