Perfect Your Health with BMI Calculator
Quickly calculate your body mass index and take the first step toward a healthier you!
BMI Calculator
Healthy BMI range: 18.5 - 25 kg/m²
Ideal weight: 132.6 - 179.2 lbs
Weight to lose: 15.8 lbs
BMI Prime: 1.09
Overview
The Body Mass Index (BMI) Calculator estimates body weight status by evaluating height and weight. It also calculates the Ponderal Index, which complements BMI (see details below).
Key Features
Switch between Metric Units (kg/cm) and US Units (lbs/feet/inches).
Categorizes weight status for adults and children.
Includes BMI Prime and Ponderal Index calculations.
What is BMI?
BMI quantifies tissue mass to assess leanness or corpulence. It categorizes individuals into weight classes (underweight, normal, overweight, obese) based on height-to-weight ratios. While widely used, BMI has limitations (see Limitations section).
BMI Categories
Adults (WHO Guidelines, Ages 20+)
| 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 | 18.5 – 25 | 0.74–1 |
| Overweight | 25 – 30 | 1–1.2 |
| Obese Class I | 30 – 35 | 1.2–1.4 |
| Obese Class II | 35 – 40 | 1.4–1.6 |
| Obese Class III | > 40 | > 1.6 |
Children & Teens (CDC Guidelines, Ages 2–20)
| Category | Percentile Range |
|---|---|
| Underweight | < 5% |
| Healthy Weight | 5% – 85% |
| At Risk of Overweight | 85% – 95% |
| Overweight | > 95% |
Health Risks
Overweight/Obese
Hypertension, high LDL cholesterol, type II diabetes.
Coronary heart disease, stroke, gallbladder disease.
Osteoarthritis, sleep apnea, certain cancers (e.g., breast, colon).
Reduced quality of life, mental health issues, higher mortality risk.
Underweight
Malnutrition, anemia, osteoporosis.
Weakened immunity, growth issues (children/teens).
Reproductive complications (e.g., miscarriage risk).
Higher mortality risk.
BMI Formulas
Metric Units
BMI=Mass (kg)Height2(m)
Example: 72.57 kg / (1.778 m)² = 23.0
US Units
BMI=703×Mass (lbs)Height2(in)
Example: 703 × (160 lbs / 70² in) = 23.0
BMI Prime
BMI Prime compares your BMI to the “normal” upper limit (25 kg/m²):
BMI Prime=BMI25
Underweight: < 0.74
Normal: 0.74 – 1
Overweight: 1 – 1.2
Obese: > 1.2
Ponderal Index (PI)
PI uses height cubed instead of squared, making it more reliable for extreme heights:
Metric Units
PI=Mass (kg)Height3(m)
US Units
PI=Height (in)Mass (lbs)3
Example: 70 in / ∛160 lbs = 12.9
Limitations of BMI
Adults:
Does not differentiate muscle vs. fat.
Less accurate for athletes (high muscle mass) or elderly (low muscle mass).
Varies by sex, ethnicity, and activity level.
Children:
Influenced by growth spurts and puberty.
BMI better identifies obesity than overweight.
General:
Use alongside other metrics (waist circumference, body fat percentage).
Conclusion
BMI is a practical screening tool for 90–95% of people but should not be the sole health indicator. Consult a healthcare provider for personalized assessments.