BMI & BMI Prime Calculator
Calculate BMI, BMI Prime, category, and healthy weight range.
References
- BMI = weight (kg) ÷ height² (m²).
- BMI Prime = BMI ÷ 25.
- Adult categories used: <18.5 underweight, 18.5–<25 normal, 25–<30 overweight, 30+ obesity classes.
Use this BMI Calculator to calculate adult body mass index, BMI Prime, BMI category, and a BMI-based healthy weight range from height and weight.
Calculation Method
For metric units:
BMI = weight (kg) ÷ height (m)²
For pounds and inches:
BMI = 703 × weight (lb) ÷ height (in)²
BMI Prime compares BMI with 25:
BMI Prime = BMI ÷ 25
The BMI-based healthy weight range is calculated from:
Lower weight = 18.5 × height²
Upper weight = 24.9 × height²
Example
For an adult weighing 70 kg and measuring 1.70 m:
BMI = 70 ÷ 1.70² ≈ 24.2
BMI Prime = 24.2 ÷ 25 ≈ 0.97
A BMI of 24.2 falls within the standard adult healthy-weight screening category.
Adult BMI Categories
- Below 18.5: Underweight
- 18.5 to below 25: Healthy weight
- 25 to below 30: Overweight
- 30 or higher: Obesity
Important Note
BMI is a screening measure and does not directly measure body fat, muscle mass, or body-fat distribution. It should be interpreted with other health information rather than used alone to diagnose health status.
Adult BMI categories are intended for people age 20 and older. Children and teens should use age- and sex-specific BMI percentiles.