BMI Calculator
Calculate Your Body Mass Index
BMI Calculator Overview
Understanding BMI
The Body Mass Index (BMI) Calculator helps determine your BMI value and corresponding weight status, taking age into account. Use the “Metric Units” tab for the International System of Units or the “Other Units” tab to convert between US and metric units. This calculator also computes the Ponderal Index, in addition to BMI, both of which are explained below.
BMI, or Body Mass Index, measures a person’s leanness or corpulence based on height and weight, serving as an indicator of tissue mass. The body mass index calculator is widely used to assess whether an individual’s body weight is healthy for their height. The resulting BMI value categorizes individuals as underweight, normal weight, overweight, or obese. These categories can vary by region and age and may include subcategories like severely underweight or very severely obese. While the BMI scale isn’t a perfect measure of health, it’s a useful screening tool to determine if further testing or lifestyle changes are necessary. Refer to the body mass index chart below for the BMI categories used by the calculator.
BMI Categories for Adults
According to the World Health Organization (WHO), here are the BMI ranges for adults, used for both men and women aged 20 or older:
Classification | BMI Range (kg/m²) |
Severe Thinness | < 16 |
Moderate Thinness | 16 – 17 |
Mild Thinness | 17 – 18.5 |
Normal | 18.5 – 25 |
Overweight | 25 – 30 |
Obese Class I | 30 – 35 |
Obese Class II | 35 – 40 |
Obese Class III | > 40 |
BMI Categories for Children and Adolescents (Ages 2-20)
The Centers for Disease Control and Prevention (CDC) provide a BMI chart for children and teens:
Category | Percentile Range |
Underweight | < 5% |
Healthy Weight | 5% – 85% |
At Risk of Overweight | 85% – 95% |
Overweight | > 95% |
Health Risks of Being Overweight
Using the obesity calculator, it’s clear that being overweight increases the risk of several serious health conditions, including:
- High blood pressure
- Elevated LDL cholesterol and triglycerides, and lower HDL cholesterol
- Type II diabetes
- Coronary heart disease
- Stroke
- Gallbladder disease
- Osteoarthritis
- Sleep apnea and breathing issues
- Certain cancers (e.g., endometrial, breast, colon)
- Reduced quality of life
- Mental health issues like depression and anxiety
- Physical pain and limited mobility
- Higher mortality risk
Maintaining a healthy BMI below 25 kg/m² is generally recommended, but consulting a doctor for personalized advice is best.
Health Risks of Being Underweight
Being underweight, as indicated by the BMI test, carries its own risks, including:
- Malnutrition, vitamin deficiencies, and anemia
- Osteoporosis
- Weakened immune system
- Growth and development issues in children and teens
- Reproductive issues and higher miscarriage risk for women
- Increased surgical complications
- Higher mortality risk
Being underweight can sometimes indicate underlying conditions such as anorexia nervosa. Medical consultation is advised if the cause of being underweight is unclear.
