About BMI Calculator
Body Mass Index (BMI) is a widely used screening tool that estimates body fat based on height and weight. Our free BMI Calculator computes your BMI in seconds using either metric (kg/cm) or imperial (lbs/in) units, and categorizes your result according to the WHO's standard ranges: Underweight, Normal weight, Overweight, Obese (Class I), and Obese (Class II+). It also shows the healthy weight range for your height.
BMI was developed by statistician Adolphe Quetelet in the 1830s and remains the most commonly used first-line screening tool in clinical settings because it requires only two easily measurable values. Doctors, nurses, nutritionists, personal trainers, and insurance companies all use BMI as a quick reference point for population health screening.
BMI has well-known limitations: it doesn't distinguish between fat mass and lean muscle mass, and it can misclassify athletic individuals with high muscle mass as overweight. It also doesn't account for age, sex, ethnicity, or fat distribution. Despite these limitations, it remains the standard screening tool for population-level health assessment and is the starting point for conversations with healthcare providers about weight-related health risks.
Our calculator shows not only your BMI value and category, but also the exact healthy weight range for your height (BMI 18.5–24.9), and the weight you would need to reach or maintain to fall within the normal category — actionable information for health goal-setting.
How to Use the BMI Calculator
Select units
Choose metric (kg and cm) or imperial (lbs and inches).
Enter your weight
Type your current weight in the selected unit.
Enter your height
Enter your height. For imperial, enter feet and inches separately.
Read your result
Your BMI, WHO category, and healthy weight range appear instantly.
Key Features & Highlights
Common Use Cases
- Check your BMI for a general health screening
- Calculate BMI before a doctor's appointment
- Track BMI changes during a weight management program
- Calculate ideal weight range for your height
- Use as part of a fitness assessment
Frequently Asked Questions
The WHO defines Normal weight as a BMI between 18.5 and 24.9. Underweight is below 18.5. Overweight is 25–29.9. Obese Class I is 30–34.9. Class II is 35–39.9. Class III (severe obesity) is 40+.
Not always. Athletes with high muscle mass may have a high BMI while having low body fat percentage. In these cases, body fat percentage measurements (DEXA scan, skinfold calipers) are more accurate.
The standard BMI formula and WHO categories are the same for both sexes. However, women naturally have a higher body fat percentage than men at the same BMI, so some clinicians use sex-adjusted thresholds.
Yes, 100% free with no hidden fees, subscriptions, or account requirements.
Everything runs client-side directly inside your web browser. No files, texts, or parameters are sent to our servers.
Yes, our tools are fully responsive and work seamlessly on iPhones, iPads, Android smartphones, and tablets.