BMI formula
BMI = weight (kg) ÷ height (m)². To convert lb to kg: divide by 2.205. To convert inches to meters: multiply by 0.0254. Categories follow WHO guidelines.
BMI calculator
Enter your weight and height to calculate your BMI and see which category you fall into.
Example
Person weighing 154 lb (70 kg) at 5'9" (175 cm): BMI = 70 ÷ (1.75²) = 22.9 → Normal weight.
What is BMI?
Body Mass Index (BMI) is a simple measure that uses weight and height to estimate whether a person is in a healthy weight range. It is widely used as an initial screening tool by health professionals worldwide, but does not account for body composition, muscle mass, or fat distribution. Consult a doctor for a full assessment.
Frequently asked questions
Is BMI accurate for athletes?
Not entirely. BMI does not distinguish between muscle and fat. Athletes with high muscle mass may have an elevated BMI even with low body fat. In those cases, additional measures like waist circumference are recommended.
What is a healthy BMI for adults?
According to the WHO, a BMI between 18.5 and 24.9 is considered normal weight. However, the ideal range may vary with age, sex, and ethnicity.
How is BMI calculated?
BMI = weight in kg ÷ (height in meters)². Example: 70 kg ÷ (1.75 m)² = 22.9.
Does a high BMI always mean obesity?
Not necessarily. BMI is a population-level screening tool, not an individual diagnosis. A doctor should evaluate other factors such as body composition, family history, and lab results.
What is the ideal weight for my height?
The ideal weight range keeps your BMI between 18.5 and 24.9. For 5'9" (175 cm), that is roughly 125–165 lb (56.7–76.3 kg).
Does BMI apply to children?
For children and adolescents, BMI-for-age percentiles are used instead of fixed thresholds. This calculator is designed for adults (18+).
How to use
- Select the unit: metric (kg/cm) or imperial (lb/in).
- Enter your weight and height.
- Your BMI and category appear instantly.
- The ideal weight range for your height is shown in the results.