BMI Calculator
Calculate your Body Mass Index (BMI) using US or Metric units. Includes category breakdowns and healthy weight ranges.
Weight in pounds (e.g., 160 lbs).
Enter height in centimeters (e.g., 178 cm, not 1.78 m).
Did you enter meters?
We calculate in centimeters. We will auto-convert your input to cm for correct mathematical output.
Weight in kilograms (e.g., 72 kg).
Your Body Mass Index
Standardized Index
WHO Guidelines Verified
⚠️ BMI Sanity Check Warning
Your calculated BMI is in an extreme clinical range (). Please verify that your weight and height inputs are correct (e.g., ensure centimeters were not confused with meters, or pounds with kilograms).
Enter height & weight to calculate your BMI
Understanding Body Mass Index (BMI)
Body Mass Index (BMI) is a standardized, widely recognized heuristic used by medical professionals, health organizations, and fitness experts to evaluate an individual's mass relative to their height. By analyzing this ratio, the index places individuals into distinct weight categories, helping determine whether a person falls within a statistically normal, underweight, overweight, or obese range.
While BMI does not measure body fat percentage directly, it correlates strongly with direct measures of body fat processing derived from hydrostatic weighing, dual-energy X-ray absorptiometry (DXA), and other clinical configurations. It serves as an accessible tool for early screening parameters to detect potential weight-related health trajectories.
The Mathematical Formulas
The underlying logic of our calculator uses standard formulas recognized globally. Depending on the input metrics selected, the systems execute calculations using the formulas below.
Metric Formula:
BMI = weight (kg) / [height (m)]²
Calculated by dividing weight in kilograms by the square of height in meters.
Imperial (US) Formula:
BMI = [weight (lbs) / (height (in))²] × 703
Calculated by dividing weight in pounds by height in inches squared, then multiplying by a conversion factor of 703.
Standardized World Health Organization Classifications
For individuals aged 20 and older, standard medical guidelines sort calculation evaluations into specific brackets established by the World Health Organization (WHO) and the CDC:
| BMI Range | Weight Category Status |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal / Healthy Weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obese Class I (Moderate) |
| 35.0 – 39.9 | Obese Class II (Severe) |
| Above 40.0 | Obese Class III (Very Severe) |
Important Clinical Limitations of BMI Profiles
Although mass index evaluation is a helpful screening metric, it should not be utilized as an all-encompassing diagnostic blueprint. Because it treats overall mass uniformly, it features baseline structural variances:
- Muscle Mass Discrepancies: Muscle tissue features significantly higher biological density parameters than fat tissue. Lean athletes or bodybuilders can be grouped into "overweight" or "obese" categories despite highly optimized body fat profiles.
- Age & Bone Density: Older adults often lose bone density parameters and functional muscle skeletal mass over time, meaning their bodies might possess higher proportional body fat values than younger adults with equivalent index profiles.
- Fat Distribution Irregularities: The calculation model is completely blind to where tissue masses are localized. Clinical data indicates that abdominal adipose tissue (visceral fat) presents far higher cardiovascular risk paradigms compared to subcutaneous fat distributed through peripheral limbs.