BMI Calculator

Calculate your Body Mass Index — metric or imperial.

Your BMI
22.9Normal
1518.5253040

BMI Calculator — What It Does

Enter your height and weight in metric (cm/kg) or imperial (ft/in/lbs) and this calculator instantly computes your Body Mass Index. It displays your BMI value, the corresponding WHO category, and a visual scale showing where you fall on the spectrum.

BMI Categories (Adults 20+)

  • Below 18.5 — Underweight
  • 18.5 – 24.9 — Normal weight
  • 25.0 – 29.9 — Overweight
  • 30.0 – 34.9 — Obese (Class I)
  • 35.0 – 39.9 — Obese (Class II)
  • 40.0 and above — Severely Obese (Class III)

Limitations of BMI

BMI is a population-level screening statistic, not a personal health diagnosis. Its key limitations:

  • Muscle vs. fat — Highly muscular people (athletes) often have high BMIs despite low body fat
  • Fat distribution — Visceral fat (around organs) is more dangerous than subcutaneous fat; BMI doesn't distinguish these
  • Age and sex — Older adults and women typically have more body fat at the same BMI as younger adults and men
  • Ethnicity — Some ethnic groups have higher health risks at lower BMI values; adjusted thresholds exist for Asian populations

Frequently Asked Questions

What is BMI and how is it calculated?
BMI (Body Mass Index) is weight in kilograms divided by height in meters squared (kg/m²). In imperial units: (weight in lbs × 703) ÷ height in inches². It's a screening tool, not a diagnostic measure.
What are the BMI categories?
Underweight: below 18.5. Normal weight: 18.5–24.9. Overweight: 25–29.9. Obese Class I: 30–34.9. Obese Class II: 35–39.9. Obese Class III (severe): 40 and above. These apply to adults aged 20+.
Is BMI an accurate measure of health?
BMI is a population-level screening tool with well-known limitations. It cannot distinguish between muscle and fat mass, so athletes often show elevated BMI. It also doesn't account for age, sex, or fat distribution.
What is a healthy BMI for children?
For people under 20, BMI is interpreted using age- and sex-specific percentile charts rather than fixed categories. A BMI at or above the 95th percentile indicates obesity in children.
What should I do if my BMI is outside the normal range?
Consult a healthcare professional for a complete assessment. BMI is just one indicator — a doctor will consider body composition, waist circumference, blood pressure, cholesterol, and other factors together.