What is BMI (Body Mass Index)?
BMI (Body Mass Index) is an internationally standardized indicator that uses the relationship between height and weight to determine whether body weight is appropriate. Devised by Belgian mathematician Adolphe Quetelet in 1832, this index is currently used by the World Health Organization (WHO) as the basic criterion for obesity assessment.
BMI is calculated by dividing weight (kg) by the square of height (m). For example, a person who is 170cm tall and weighs 65kg has a BMI of 65 / (1.70)^2 = 22.49. This value is used to classify underweight, normal, overweight, and obesity.
Key Features
Instant BMI Calculation
Simply enter your height and weight to get your BMI calculated in real-time with instant results.
Visual BMI Gauge
Intuitively see your current BMI position on a color gradient bar from blue to red.
WHO Classification
Provides 6-level obesity classification based on official World Health Organization (WHO) standards.
Normal Weight Range
Shows the normal weight range (BMI 18.5-24.9) based on your entered height.
Unit Conversion (kg↔lb, cm↔ft)
Freely switch between metric and imperial units to calculate in your preferred measurement system.
Child/Adolescent BMI
Ages 2-19 are assessed using WHO BMI-for-age percentile criteria adjusted for age and sex.
How to Use
- Enter Height — Enter your height in the height (cm) field. (e.g. 170)
- Enter Weight — Enter your current weight in the weight (kg) field. (e.g. 65)
- Click Calculate — Press the 'Calculate BMI' button to see results.
- Check Results — Review your BMI value, obesity classification, and normal weight range.
Use Cases
Setting Diet Goals
Check your current BMI and set a healthy diet plan targeting a weight within the normal range.
Pre-Health Checkup
Calculate your BMI before a health checkup to assess the need for obesity-related tests in advance.
Exercise Program Design
Use BMI results as reference to create a customized exercise plan for weight loss or muscle gain.
Weight Change Tracking
Regularly measure your BMI to numerically track weight management results and maintain motivation.
Frequently Asked Questions
Does a normal BMI mean I'm healthy?
BMI is calculated solely from the ratio of weight to height, so it doesn't reflect muscle mass, body fat percentage, or visceral fat. Even with a normal BMI, body fat percentage may be high. For an accurate health assessment, it's recommended to get a comprehensive evaluation at a medical facility.
Do muscular people get a high BMI?
Yes, since BMI is calculated only from weight and height, athletes and bodybuilders with high muscle mass may show overweight or obese BMI values. In such cases, measuring body fat percentage alongside BMI provides a more accurate picture.
Do the same BMI criteria apply to children and adolescents?
No. Since children and adolescents are still growing, adult BMI criteria cannot be directly applied. For pediatric populations, obesity is determined by percentile compared to others of the same age and sex.
Are BMI criteria different for Asians?
While WHO general criteria are universal, Asians tend to have a higher body fat percentage at the same BMI. Some Asian countries classify BMI 23+ as overweight and 25+ as obese. This calculator uses international WHO standards.
Is my data safe with this calculator?
Yes, all calculations are processed in your browser and your height and weight information is never sent to any server. BMI history is stored only in your browser's localStorage and can be deleted at any time.
What criteria does the child mode use?
The child (2-19 years) mode uses WHO BMI-for-age percentile criteria. Compared to children of the same age and sex, below the 5th percentile is underweight, 5th-84th is normal, 85th-94th is overweight, and 95th percentile or above is obese.
Can I calculate in pounds and feet?
Yes, use the unit toggle (kg/cm ↔ lb/ft) at the top to enter height in feet/inches and weight in pounds. The calculator internally converts to metric units for accurate BMI calculation.
Privacy Notice
This BMI calculator processes all calculations in your browser. Your health data is never transmitted to any server. BMI history is stored only in your browser's localStorage and can be deleted at any time with the 'Clear History' button.