BMI Calculator
Calculate your Body Mass Index (BMI) with detailed metrics like BMI Prime and Ponderal Index.
Your BMI Chart
Visualize your BMI in the context of WHO categories for adults.
BMI Introduction
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BMI measures a person's leanness or corpulence based on height and weight, quantifying tissue mass. It's a general indicator of healthy body weight, categorizing individuals as underweight, normal, overweight, or obese. While imperfect, BMI is useful for identifying if further health assessments are needed.
BMI Table for Adults
World Health Organization's BMI categories for adults (age 20+).
| 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 Table for Children and Teens (Age 2-20)
CDC's BMI-for-age percentile ranges for children and teens.
| Category | Percentile Range |
|---|---|
| Underweight | < 5% |
| Healthy weight | 5% - 85% |
| At risk of overweight | 85% - 95% |
| Overweight | > 95% |
Risks of Being Overweight
According to the CDC, being overweight increases risks such as:
- High blood pressure
- High LDL cholesterol, low HDL cholesterol, high triglycerides
- Type II diabetes
- Coronary heart disease
- Stroke
- Gallbladder disease
- Osteoarthritis
- Sleep apnea
- Certain cancers (endometrial, breast, colon, kidney, gallbladder, liver)
- Low quality of life
- Mental illnesses (depression, anxiety)
- Body pains and physical function difficulties
- Increased mortality risk
Risks of Being Underweight
Underweight individuals may face risks like:
- Malnutrition, vitamin deficiencies, anemia
- Osteoporosis
- Decreased immune function
- Growth and development issues
- Reproductive issues for women
- Surgical complications
- Increased mortality risk
Limitations of BMI
BMI measures excess weight, not fat, and is influenced by age, sex, ethnicity, and muscle mass. For example:
- Older adults may have more fat at the same BMI.
- Women tend to have more fat than men.
- Athletes may have higher BMIs due to muscle.
- In children, BMI varies with height and maturation.
BMI is indicative for 90-95% of people but should be used with other metrics.
BMI Formula
Metric units:
BMI = mass (kg) / height² (m)
US units:
BMI = 703 × mass (lbs) / height² (in)
BMI Prime
BMI Prime is the ratio of BMI to the normal range upper limit (25 kg/m²):
BMI Prime = BMI / 25
Ranges: <0.74 (underweight), 0.74-1 (normal), 1-1.2 (overweight), >1.2 (obese).
Ponderal Index
The Ponderal Index (PI) uses:
PI = mass (kg) / height³ (m)
It’s more reliable for very tall or short individuals.