BMI Calculator – Calculate Your Body Mass Index
Your BMI result falls into one of four main categories that help assess weight status. A BMI below 18.5 is considered underweight, while a BMI between 18.5 and 24.9 indicates normal weight. If your BMI falls between 25 and 29.9, you're classified as overweight, and a BMI of 30 or higher places you in the obese category. These ranges are based on population studies that correlate BMI values with health risks.
While BMI is a useful screening tool for general health assessments, it's important to understand its limitations. BMI doesn't distinguish between muscle mass and fat mass, which means very muscular individuals may be classified as overweight or obese despite having low body fat. Additionally, BMI doesn't account for differences in body composition between men and women, or changes that occur with aging.
Consider your BMI result as one piece of health information rather than a definitive measure of your health status. Factors like waist circumference, overall fitness level, diet quality, and family health history provide a more complete picture. If you have concerns about your weight or health, consult with a healthcare professional who can evaluate your individual circumstances and provide personalized guidance.
How BMI is Calculated
Metric: BMI = weight (kg) ÷ height (m)²
Imperial: BMI = (weight (lbs) × 703) ÷ height (in)²
For example, a person who is 1.75m tall and weighs 70kg has a BMI of 70 ÷ (1.75)² = 22.9, which falls in the normal weight range.
Frequently Asked Questions
What is a healthy BMI range?
A BMI between 18.5 and 24.9 is generally considered healthy for adults. However, BMI doesn't distinguish between muscle and fat mass, so athletes may have a higher BMI while still being healthy.
Is BMI accurate for everyone?
BMI is a useful screening tool for most adults but has limitations. It may overestimate body fat in muscular individuals and underestimate it in older adults who have lost muscle mass. It's best used alongside other health indicators.
How often should I check my BMI?
For most adults, checking BMI a few times per year is sufficient. If you're actively working on weight management, monthly checks can help track progress. Always consult a healthcare provider for personalized advice.
Does BMI apply to children?
For children and teens (ages 2-20), BMI is calculated the same way but interpreted using age- and sex-specific percentiles rather than fixed categories, since body composition changes significantly during growth.
What should I do if my BMI is outside the healthy range?
If your BMI suggests you're underweight or overweight, consider consulting a healthcare provider. They can assess your overall health using additional measurements and recommend appropriate lifestyle changes if needed.