BMI Calculator
Calculate your Body Mass Index (BMI) instantly. Enter your weight and height to compare the result with adult BMI categories.
Examples
Normal weight adult
A 70 kg person who is 175 cm tall.
- Weight
- 154.324 lb
- Height
- 68.898 in
Your BMI
22.9 kg/m²
Category
Normal
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How It Works
Formula
Variables, symbols and units
- Body Mass Index(kg/m²)
- Body weight(kg)
- Height(m)
Calculation method explained
BMI is calculated by dividing your body weight in kilograms by the square of your height in metres. The resulting number is compared against adult BMI category ranges. While BMI is a useful screening tool, it does not directly measure body fat or account for factors like age, sex, ethnicity, or muscle mass.
Examples
Normal weight adult154.324 lb · 68.898 in → 22.9 kg/m²
A 70 kg person who is 175 cm tall.
- Weight
- 154.324 lb
- Height
- 68.898 in
- Your BMI
- 22.9 kg/m²
Overweight check187.393 lb · 66.929 in → 29.4 kg/m²
An 85 kg person who is 170 cm tall.
- Weight
- 187.393 lb
- Height
- 66.929 in
- Your BMI
- 29.4 kg/m²
Underweight check110.231 lb · 70.866 in → 15.4 kg/m²
A 50 kg person who is 180 cm tall.
- Weight
- 110.231 lb
- Height
- 70.866 in
- Your BMI
- 15.4 kg/m²
Frequently Asked Questions
What is a healthy BMI range?
CDC adult BMI categories classify 18.5 to less than 25 as healthy weight. Values below 18.5 are underweight, 25 to less than 30 are overweight, and 30 or higher is obesity.
Is BMI accurate for athletes?
BMI does not distinguish between muscle mass and fat mass. Athletes with significant muscle may register as overweight or obese despite having low body fat. For a more complete picture, consider complementary measures like waist circumference or body fat percentage.
Does BMI differ for men and women?
The standard adult BMI formula and category thresholds are the same for adult men and women. Sex, age, ethnicity, and muscle mass can affect how BMI relates to body fat, so context matters when interpreting the result.
Can I use BMI for children?
Children and teenagers use age- and sex-specific BMI-for-age percentiles rather than the adult thresholds. A pediatrician can help interpret a child's BMI correctly with the appropriate growth chart.
How often should I check my BMI?
For most adults, checking BMI once every few months is sufficient. If you are actively trying to gain or lose weight, monthly checks can help you track progress, but daily fluctuations in weight make more frequent checks unreliable.