BMI Calculator
Calculate your Body Mass Index. Visual gauge, WHO category, normal weight range for your height.
Your measurements
Everything about BMI calculation
Why calculate your BMI?
Body Mass Index (BMI) is the reference indicator used by the WHO to assess adult body composition. It quickly shows how your weight relates to your height and identifies potential health risks.
Our calculator displays a color-coded visual gauge with WHO categories (underweight, normal, overweight, obesity classes I-III) and calculates your normal weight range. It supports metric and imperial units.
Free, no registration required, and privacy-friendly: no data is sent to any server. All calculations run in your browser.
Who uses this calculator?
- Individuals
- Track your BMI as part of a fitness program or weight management plan.
- Healthcare professionals
- Quickly calculate a patient's BMI for initial nutritional screening during consultations.
- Fitness coaches
- Assess clients' body composition to tailor training and nutrition programs.
- Medical/nutrition students
- Understand WHO categories and the relationship between weight, height, and associated health risks.
How to use the BMI calculator
Enter your height in centimeters (or feet/inches) and your weight in kilograms (or pounds).
The calculator instantly displays your BMI, the corresponding WHO category, and the visual gauge.
Check the normal weight range calculated for your height to set a realistic goal.
Frequently asked questions
- How is BMI calculated?
- BMI is calculated by dividing weight (kg) by height squared (m): BMI = weight / height². For example, a 70 kg person who is 1.75 m tall has a BMI of 70 / (1.75²) = 22.9 kg/m².
- What are the BMI categories according to the WHO?
- The WHO defines: underweight (BMI < 18.5), normal weight (18.5–24.9), overweight (25–29.9), obesity class I (30–34.9), class II (35–39.9), and class III (≥ 40). These thresholds apply to adults aged 18 and over.
- Is BMI reliable for everyone?
- BMI is a useful but limited statistical indicator. It doesn't distinguish between fat mass and muscle mass. A muscular athlete may have a high BMI without excess fat. It's not suitable for children, pregnant women, or elderly people without adjustment.
- What is the ideal BMI?
- A BMI between 18.5 and 24.9 is considered normal by the WHO. However, optimal BMI depends on individual factors like age, sex, body type, and muscle mass. Consult a healthcare professional for personalized assessment.
- Is my data confidential?
- Yes. No personal data is transmitted or stored. The calculation runs locally in your browser. Your weight and height never leave your device.
Understanding Body Mass Index
What is Body Mass Index (BMI)?
BMI is a biometric indicator invented by Adolphe Quetelet in the 19th century. It relates a person's weight and height via the formula weight/height². The WHO uses it as a screening tool for overweight and obesity in adult populations. A normal BMI falls between 18.5 and 24.9 kg/m². Above 30, it's classified as obesity, a risk factor for type 2 diabetes, cardiovascular disease, and certain cancers.
What are the limitations of BMI as a health indicator?
BMI doesn't directly measure body fat or its distribution. Abdominal (visceral) fat is more dangerous than subcutaneous fat, but BMI doesn't make this distinction. Complementary indicators like waist circumference, waist-to-hip ratio, or body composition analysis (bioimpedance, DEXA) provide a more accurate picture. BMI remains the best rapid screening tool at the population level.
How does BMI vary by age and sex?
WHO thresholds are the same for adult men and women, but women naturally have a higher body fat percentage at the same BMI. For children and adolescents, BMI is interpreted using age- and sex-specific growth charts (percentiles). In elderly people, a slightly higher BMI (23-27) is sometimes associated with better survival, a phenomenon called the 'obesity paradox'.