BMI Calculator — Calculate Your Body Mass Index Free
Calculate your Body Mass Index instantly in metric (kg/cm) or imperial (lb/ft+in). See your BMI category with a visual gauge, your healthy weight range for your height, BMI Prime, Ponderal Index, and a target weight calculator to reach any goal BMI.
100% private. All calculations run locally in your browser. No data is collected or transmitted.
How to Calculate Your BMI
- 01
Choose metric or imperial
Switch between kg/cm and lb/ft+in. All conversions happen automatically.
- 02
Enter weight and height
Input your measurements. The BMI result, category badge, and gauge update instantly.
- 03
Explore your results
See your healthy weight range, BMI Prime, Ponderal Index, and set a target BMI to calculate goal weight.
Frequently Asked Questions
What is BMI and how is it calculated?
BMI (Body Mass Index) is a value calculated from a person's weight and height. The formula is: BMI = weight (kg) ÷ height² (m²). For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9.
What is a healthy BMI range?
According to the World Health Organization (WHO), a BMI between 18.5 and 24.9 is considered normal weight. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese. These categories apply to adults aged 18 and over.
Is BMI accurate for everyone?
BMI is a population-level screening tool, not a perfect individual measure. It can overestimate body fat in athletes with high muscle mass and underestimate it in elderly people who have lost muscle. It also does not account for fat distribution. Despite limitations, it remains the most widely used screening tool due to its simplicity.
What is BMI Prime?
BMI Prime is the ratio of your BMI to the upper limit of the normal BMI range (25). A BMI Prime of 1.0 corresponds to BMI 25. Values below 1.0 indicate normal or underweight, above 1.0 indicates overweight. It provides a quick percentage-above-normal indicator.
What is the difference between BMI and Ponderal Index?
While BMI divides weight by height squared (kg/m²), the Ponderal Index divides weight by height cubed (kg/m³). The Ponderal Index is considered more accurate for very tall or very short individuals because it better accounts for how body mass scales with height. A normal Ponderal Index range is approximately 11–15 kg/m³.