BMI Calculator

Calculate your Body Mass Index (BMI) to see if you're at a healthy weight. Get personalized results based on your height and weight.

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What is BMI (Body Mass Index)?

Body Mass Index (BMI) is a simple, internationally recognized health metric that uses your weight and height to estimate total body fat. It is typically used as a screening tool by healthcare providers to identify potential weight categories that may lead to health problems.

How is BMI Calculated?

The BMI formula is universally standard, though it differs slightly based on the measurement system you use:

  • Metric System: BMI = Weight (kg) / [Height (m)]²
  • Imperial System: BMI = Weight (lbs) / [Height (in)]² × 703

Standard BMI Categories

According to the World Health Organization (WHO), adult BMI is divided into the following categories:

  • Underweight: Less than 18.5
  • Normal weight: 18.5 – 24.9
  • Overweight: 25.0 – 29.9
  • Obesity: 30.0 or greater

Limitations of BMI

While BMI is a useful general guideline, it is not a diagnostic tool and has several well-documented limitations. Because BMI only uses weight and height, it does not distinguish between muscle mass, bone density, and body fat. For instance, athletes and bodybuilders with high muscle mass may have a "high" BMI while having very low body fat percentages. Older adults who have lost muscle mass may fall into a "normal" BMI range despite having excess body fat. Always consult a healthcare professional for a comprehensive health assessment.

Frequently Asked Questions

What is a healthy BMI range?
A healthy BMI range is 18.5–24.9 according to the World Health Organization. Below 18.5 is considered underweight, 25–29.9 is overweight, and 30+ is obese. However, BMI is a screening tool, not a diagnostic test. Athletes with high muscle mass may have a high BMI despite low body fat, while older adults may have normal BMI but excess body fat. Always consult a healthcare provider for a comprehensive health assessment.
How accurate is BMI for measuring body fat?
BMI has well-documented limitations. It does not distinguish between muscle mass, bone density, and body fat. A 2016 study in the International Journal of Obesity found that BMI misclassifies about 50% of people with excess body fat. For a more accurate picture, consider body fat percentage, waist-to-height ratio, or consult your doctor for professional body composition testing.
Does BMI account for age and gender?
The standard BMI formula uses only height and weight, not age or gender. However, body composition naturally changes with age — muscle mass declines and body fat tends to increase. The same BMI may mean different things for a young athlete versus an older adult. Women naturally have higher body fat percentages than men, but the standard BMI categories are the same for both.
What is the difference between BMI and body fat percentage?
BMI estimates body fat based on height and weight only, while body fat percentage directly measures the proportion of fat mass versus lean mass. Body fat percentage can be measured using methods like skinfold calipers, bioelectrical impedance, DEXA scans, or the US Navy circumference method. For most people, BMI is a useful screening tool, but body fat percentage provides a more accurate picture of body composition.

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