Height to Weight BMI Calculator
Calculate BMI, BMI Prime, and Ponderal Index considering age, sex, and international WHO or CDC percentile standards.
Your Body Mass Analysis
Complete Solved Method & Calculations
BMI Introduction
Body Mass Index (BMI) is a measurement of a person’s leanness or corpulence based on their height and weight, intended to quantify tissue mass. It is widely used as a general indicator of whether a person has a healthy body weight for their height.
BMI Table for Adults (Age 20+)
This is the World Health Organization’s (WHO) recommended body weight classification based on BMI values for adults age 20 or older:
| Classification | BMI Range (kg/m²) | BMI Prime |
|---|---|---|
| Severe Thinness | < 16 | < 0.64 |
| Moderate Thinness | 16 – 17 | 0.64 – 0.68 |
| Mild Thinness | 17 – 18.5 | 0.68 – 0.74 |
| Normal Weight | 18.5 – 25 | 0.74 – 1.0 |
| Overweight | 25 – 30 | 1.0 – 1.2 |
| Obese Class I | 30 – 35 | 1.2 – 1.4 |
| Obese Class II | 35 – 40 | 1.4 – 1.6 |
| Obese Class III | > 40 | > 1.6 |
BMI Table for Children and Teens (Age 2–20)
The Centers for Disease Control and Prevention (CDC) recommends BMI categorization for children and adolescents based on age and sex percentiles:
| Category | Percentile Range |
|---|---|
| Underweight | < 5th percentile |
| Healthy weight | 5th – 85th percentile |
| At risk of overweight | 85th – 95th percentile |
| Overweight / Obese | > 95th percentile |
Risks Associated with Being Overweight
According to the CDC, higher body fat can increase risks of high blood pressure, elevated bad LDL cholesterol, Type II diabetes, coronary heart disease, stroke, sleep apnea, osteoarthritis, and clinical depression.
Risks Associated with Being Underweight
Being underweight is linked to malnutrition, vitamin deficiencies, anemia, osteoporosis, decreased immune function, growth delays in children, and reproductive issues in women.
Limitations of BMI
BMI cannot measure body composition or differentiate between fat mass and muscle mass. Older adults naturally carry more fat than younger adults at the same BMI, women carry more fat than men at equivalent BMIs, and bodybuilders or athletes may record high BMIs despite low body fat.
BMI Prime & Ponderal Index
BMI Prime represents the ratio of measured BMI to the normal upper limit ($25\text{ kg/m}^2$). A value below $0.74$ indicates underweight, $0.74–1.0$ is normal, and above $1.0$ is overweight.
The Ponderal Index (PI) cubes height instead of squaring it ($\text{PI} = \text{mass} / \text{height}^3$), offering a more reliable body mass indicator for extremely tall or short individuals.
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