BMI Calculator (kg)
The body mass index (BMI) estimates your body fat using weight and height. The calculator above uses your weight in kilograms and height in centimeters to instantly compute your BMI and display your weight category according to World Health Organization (WHO) guidelines.
How BMI Is Calculated Using Kilograms and Meters
The metric BMI formula divides your weight in kilograms by your height in meters squared.
Formula:
BMI = weight (kg) / [height (m)]²
If your height is in centimeters, first convert it to meters by dividing by 100. For instance, 170 cm becomes 1.70 m.
Example calculations:
A person weighing 70 kg with a height of 170 cm (1.70 m):
BMI = 70 / (1.70 × 1.70) = 70 / 2.89 = 24.2 (normal weight).A person weighing 90 kg with a height of 175 cm (1.75 m):
BMI = 90 / (1.75 × 1.75) = 90 / 3.06 = 29.4 (overweight).
The calculator performs these steps automatically as soon as you provide your weight and height.
BMI Categories and What They Mean
The World Health Organization defines the following BMI ranges for adults aged 20 and older. These cutoffs are used internationally to classify weight status.
| BMI (kg/m²) | Weight Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity class I |
| 35.0 – 39.9 | Obesity class II |
| 40.0 and above | Obesity class III |
A normal‑weight BMI is linked to the lowest risk of weight‑related health problems. Moving into the overweight or obese categories raises the likelihood of type 2 diabetes, cardiovascular disease, and other conditions. An underweight result may indicate nutritional deficiencies or underlying health issues.
Keep in mind that BMI is a screening tool, not a diagnosis. It does not distinguish between muscle and fat, so athletes may record a high BMI without excess body fat.
Why Use a BMI Calculator in Kilograms?
Most countries use kilograms and centimeters for medical measurements. A calculator that works directly in metric units removes the need to convert from pounds or stones and gives a result that matches the numbers on your scale and measuring tape.
The metric system is also the standard for BMI research, making it easy to compare your results with large‑scale population data from the WHO or national health services. If you track your weight in kilograms, this calculator delivers consistent and repeatable BMI values.
Disclaimer: This calculator provides an estimate and should not replace professional medical advice.