BMI Calculator

Calculate your Body Mass Index (BMI) by using the form below. Enter your weight and height and we'll give you immediate results.

Age ages: 2 - 120

Gender Male Female

Height

feet inches

Weight

pounds

Age ages: 2 - 120

Gender Male Female

Height

cm

Weight

kg

Your Results

BMI = 23 kg/m² (Normal)

BMI = 23

Underweight Normal Overweight Obese

Healthy BMI range: 18.5 kg/m² - 25 kg/m²

Healthy weight for your height: 128.9 lbs - 174.2 lbs

BMI Prime: 0.92

Ponderal Index: 12.9 kg/m³

Body Mass Index (BMI) is a numerical measurement derived from an individual's height and weight that serves as a general indicator of healthy body weight. While BMI doesn't directly measure body fat, it correlates with more direct measures of body fat and provides a simple, standardized assessment tool.

Key Points About BMI:

- Calculated using weight and height measurements

- Provides a general weight status category
- Used for adults, children, and adolescents
- Should be interpreted differently for children (using percentiles)
- Has limitations (discussed in detail below)

BMI Calculation Methods

Standard Formulas:

Measurement System	Formula	Example Calculation
Metric Units	BMI = weight (kg) / [height (m)]²	72.57 kg / (1.778 m)² = 23.0
US Units	BMI = 703 × weight (lbs) / [height (in)]²	703 × 160 lbs / (70 in)² = 23.0

BMI Classification Tables

For Adults (Age 20+):

Classification	BMI Range (kg/m²)	BMI Prime Range	Health Risk
Severe Thinness	< 16	< 0.64	High
Moderate Thinness	16 - 17	0.64 - 0.68	Moderate
Mild Thinness	17 - 18.5	0.68 - 0.74	Mild
Normal weight	18.5 - 25	0.74 - 1	Minimal
Overweight	25 - 30	1 - 1.2	Increased
Obese Class I	30 - 35	1.2 - 1.4	High
Obese Class II	35 - 40	1.4 - 1.6	Very High
Obese Class III	> 40	> 1.6	Extremely High

For Children & Teens (Age 2-19):

Category	Percentile Range
Underweight	< 5th percentile
Healthy weight	5th - 85th percentile
At risk of overweight	85th - 95th percentile
Overweight	> 95th percentile

Additional Metrics

BMI Prime

BMI Prime is a dimensionless number that represents the ratio of a person's BMI to the upper limit of normal BMI (25 kg/m²):

text

BMI Prime = BMI / 25

Ponderal Index

The Ponderal Index (PI) is similar to BMI but uses height cubed instead of squared:

Measurement System	Formula	Example
Metric	PI = weight (kg) / [height (m)]³	72.57 / (1.778)³ = 12.9
US Units	PI = height (in) / ∛weight (lbs)	70 / ∛160 = 12.9

Health Risks Associated with Weight Status

Risks of Being Overweight/Obese:

Category	Potential Health Consequences
Cardiovascular	High blood pressure, coronary heart disease, stroke
Metabolic	Type 2 diabetes, high cholesterol, high triglycerides
Musculoskeletal	Osteoarthritis, joint problems
Respiratory	Sleep apnea, breathing difficulties
Other	Certain cancers, reduced quality of life, increased mortality

Risks of Being Underweight:

Category	Potential Health Consequences
Nutritional	Malnutrition, vitamin deficiencies, anemia
Skeletal	Osteoporosis, increased fracture risk
Immune	Decreased immune function
Reproductive	Menstrual irregularities, fertility issues
Other	Surgical complications, increased mortality

Limitations of BMI

While useful for population-level assessments, BMI has several important limitations:

Limitation	Explanation
Body Composition	Doesn't distinguish between muscle and fat
Age Differences	Older adults may have more fat at same BMI
Gender Differences	Women typically have more body fat than men at same BMI
Ethnic Variations	BMI thresholds may differ by ethnicity
Athletes	May be classified as overweight due to muscle mass
Height Extremes	Less accurate for very tall or short individuals

Interpretation Guidelines

1. For most adults, BMI provides a reasonable estimate of body fat

2. Should be used as a screening tool, not a diagnostic measure

3. Always consider in context with other health indicators

4. Children's BMI must be interpreted using age- and sex-specific percentiles

5. Consult healthcare professionals for personalized assessments