Calculate your Body Mass Index (BMI) by using the form below. Enter your weight and height and we’ll give you immediate results.
Your Results
BMI = 23 kg/m² (Normal)
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
BMI Categories
| Classification | BMI Range (kg/m²) | Health Risk |
|---|---|---|
| Underweight | < 18.5 | High |
| Normal weight | 18.5 – 24.9 | Minimal |
| Overweight | 25 – 29.9 | Increased |
| Obese Class I | 30 – 34.9 | High |
| Obese Class II | 35 – 39.9 | Very High |
| Obese Class III | > 40 | Extremely High |
About BMI
Body Mass Index (BMI) is a person’s weight in kilograms divided by the square of height in meters. BMI is an inexpensive and easy screening method for weight category—underweight, healthy weight, overweight, and obesity.
Limitations of BMI
BMI is a useful measurement for most people over 18 years old. But it is only an estimate and doesn’t take into account age, ethnicity, gender, and body composition. Athletes with high muscle mass may have a high BMI without increased health risks. Older adults may have more body fat than younger adults with the same BMI.
Introduction to BMI
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
- For most adults, BMI provides a reasonable estimate of body fat
- Should be used as a screening tool, not a diagnostic measure
- Always consider in context with other health indicators
- Children's BMI must be interpreted using age- and sex-specific percentiles
- Consult healthcare professionals for personalized assessments
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