02/09/2026
BMI Calculator
| Category | BMI Range |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese | 30.0 and above |
What is BMI Calculator?
Body Mass Index (BMI) is a simple screening measure that relates your weight to your height. This calculator supports both metric (centimetres/kilograms) and imperial (feet-inches/pounds) units, and adds your healthy weight range, BMI Prime, Ponderal Index and — if you enter your age and sex — an estimated body fat percentage.
How to use BMI Calculator
Choose Metric or Imperial units, then enter your height and weight. Age and sex are optional — add them to also see an estimated body fat percentage. The BMI value and its category (Underweight, Normal weight, Overweight or Obese) update as you type.
Formula
Example
A person who is 170 cm tall and weighs 65 kg has a height of 1.70 m, so BMI = 65 ÷ (1.70 × 1.70) = 65 ÷ 2.89 ≈ 22.5, which falls in the "Normal weight" range.
Understanding your result
BMI is a general population-level screening tool, not a diagnosis. It does not account for muscle mass, bone density, age or body composition, so athletes and older adults in particular may see results that do not reflect their actual health. The body fat % is likewise an estimate from a population formula, not a direct measurement.
Frequently Asked Questions
What BMI range is considered normal?
The commonly used WHO ranges are: below 18.5 underweight, 18.5–24.9 normal weight, 25–29.9 overweight, and 30+ obese. This tool follows those ranges for reference only.
Is BMI accurate for everyone?
No — it is a general estimate. It can be misleading for very muscular people, pregnant women, children, and the elderly. Speak with a healthcare professional for a proper assessment.
Can I use feet/inches and pounds?
Yes — switch to the "Imperial (ft-in / lbs)" toggle above the height and weight fields to enter your height in feet and inches and your weight in pounds. The results (including the healthy weight range) are shown in the matching unit.
Why does BMI not change under 20 the way I expect?
Standard adult BMI categories aren't reliable for children and teens under 20 — a note appears below your result recommending BMI-for-age growth-chart percentiles instead, which this calculator does not compute.