The BMI calculator computes your Body Mass Index from height and weight, shows which weight category you fall into, and gives you the healthy weight range for your height. Input is accepted for ages 1–130, heights 10–200 cm, and weights 1–500 kg.
The formula and thresholds used
BMI = weight (kg) ÷ height² (m)
Height is entered in centimeters; the tool converts to meters internally. The four categories and their exact cutoffs:
| Category | BMI range |
|---|---|
| Underweight | below 18.5 |
| Normal | 18.5 – 24.9 |
| Overweight | 24.9 – 28.0 |
| Obese | 28.0 and above |
The color bar at the bottom spans blue through red across the same scale, with tick marks at 18.5, 24.0, and 28.0.
How the recommended weight range is calculated
The "recommended weight" output shows the lower and upper ends of the BMI 18.5–24.9 band at your current height:
- Lower bound = 18.5 × height(m)²
- Upper bound = 24.9 × height(m)²
For a person 170 cm tall: 18.5 × 1.70² = 53.5 kg and 24.9 × 1.70² = 72.0 kg. This is a reference range only.
Where BMI falls short
BMI is a ratio of weight to height and cannot distinguish fat from muscle. Practical cases where the number misleads:
- Athletes with high muscle mass often read as overweight or obese despite low body fat
- The thresholds this tool uses (24.9 / 28.0) sit between the WHO standard (25.0 / 30.0) and the stricter Asian standard (23.9 / 27.9) — if your doctor uses a different cutoff, the category label here may differ
- Children under 18, pregnant women, and adults over 70 should not use adult BMI thresholds for health decisions