Calculate your Body Mass Index instantly. Supports metric (cm/kg) and imperial (in/lbs) units — free and no sign-up required.
Body Mass Index (BMI) is a quick screening measure that uses your height and weight to estimate whether you are underweight, at a normal weight, overweight, or obese. It is one of the most widely used health indicators and requires no equipment beyond a scale and a measuring tape.
To use the calculator, pick your preferred unit system, enter your height and weight, then press Calculate BMI. Your result appears immediately with its category and a visual scale so you can see where you sit.
BMI is a screening tool, not a diagnosis. For a full health picture, consult a healthcare professional who can consider muscle mass, age, and other factors.
The World Health Organization (WHO) classifies adult BMI into four categories. Ranges below use standard international cut-offs.
| Category | BMI Range | Health Note |
|---|---|---|
| Underweight | Below 18.5 | May indicate nutritional deficiency or low body mass. |
| Normal weight | 18.5 – 24.9 | Generally associated with the lowest health risk. |
| Overweight | 25.0 – 29.9 | Increased risk of weight-related conditions. |
| Obese | 30.0 and above | Higher risk of cardiovascular and metabolic conditions. |
Divide your weight in kilograms by the square of your height in meters (kg/m²). For imperial, use the formula (weight in pounds × 703) ÷ height in inches². Enter your height and weight above and the calculator does it instantly.
A BMI between 18.5 and 24.9 is considered a normal, healthy range for most adults. Below 18.5 is underweight, 25.0–29.9 is overweight, and 30.0 or above is classified as obese.
BMI is a useful screening tool but does not measure body fat directly. Muscular athletes, older adults, and pregnant women may show a BMI that does not reflect their true health. Use it alongside waist circumference and other health indicators.
The metric formula uses kilograms and meters (kg/m²). The imperial formula uses pounds and inches and applies a 703 conversion factor. Both produce the same BMI value when converted correctly.
Yes. For metric, square your height in meters, then divide your weight in kg by that number. For example, 65 kg ÷ (1.70 × 1.70) = 22.5. A calculator just makes it faster and error-free.