BMI Calculator
Calculate your Body Mass Index (BMI) based on weight and height to assess whether you are underweight, normal weight, overweight, or obese.
Results
Visualization
How It Works
Body Mass Index (BMI) is a simple screening metric that uses your weight and height to estimate body fatness. While it does not measure body fat directly, BMI correlates with more direct measures and is widely used by healthcare providers to identify potential weight-related health risks.
The Formula
Variables
- weight — Body weight in kilograms
- height — Height in meters (converted from cm by dividing by 100)
- BMI — The resulting Body Mass Index value
Worked Example
For a person weighing 70 kg and standing 170 cm tall: height in meters = 1.70, so BMI = 70 / (1.70 x 1.70) = 70 / 2.89 = 24.2. This falls in the 'Normal weight' category (18.5 to 24.9).
Practical Tips
- BMI does not distinguish between muscle and fat, so very muscular individuals may have a high BMI but low body fat.
- Use BMI as a starting point, not a definitive diagnosis. Pair it with waist circumference or body fat percentage for a fuller picture.
- A normal BMI range is 18.5 to 24.9 for most adults regardless of age or sex.
- BMI categories may not apply equally to all ethnic groups; some populations face higher health risks at lower BMI values.
- Track your BMI over time rather than focusing on a single measurement to spot meaningful trends.
Frequently Asked Questions
Is BMI accurate for athletes?
BMI can overestimate body fat in athletes and people with high muscle mass. If you exercise regularly and carry significant muscle, consider using body fat percentage or waist-to-hip ratio for a more accurate assessment.
Does BMI apply to children?
Children and teens use age- and sex-specific BMI percentiles rather than the adult categories. A pediatrician can plot your child's BMI on a growth chart to determine their weight status.
What BMI is considered healthy?
A BMI between 18.5 and 24.9 is classified as normal weight by the WHO. However, health depends on many factors beyond BMI, including diet, activity level, and family history.
Can BMI predict disease risk?
Higher BMI is associated with increased risk of heart disease, type 2 diabetes, and certain cancers. However, BMI alone cannot diagnose any condition. Your doctor will consider BMI alongside blood pressure, cholesterol, and other markers.
How often should I check my BMI?
Checking BMI once every few months is sufficient for most adults. More frequent monitoring may be useful if you are actively trying to gain or lose weight under medical supervision.