Body Mass Index (BMI) Calculator: Based on Your Height and Weight

What is Body Mass Index (BMI)?

Body Mass Index is a simple ratio used to assess your weight relative to your height. It's calculated by dividing your weight (kg) by the square of your height in meters: BMI = weight (kg) ÷ height (m)². For example, someone weighing 70 kg at 1.70 m has a BMI of 70 ÷ 2.89 ≈ 24.2.

BMI is a standard method healthcare professionals use to quickly screen weight status. Our tool calculates the value and shows the result along with its category; it never asks for information such as your name or email.

BMI categories and ranges

The World Health Organization uses the following ranges for adults:

• Below 18.5: underweight (our tool also breaks this down into mild, moderate and severe)
• 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

Why does BMI matter?

A high BMI is associated with increased risk of conditions such as type 2 diabetes, high blood pressure, cardiovascular disease, sleep apnea, and joint problems. A very low BMI can be linked to malnutrition, reduced bone density, and weakened immunity. In women, both very low and high BMI can affect menstrual regularity and fertility — so weight changes shouldn't be ignored.

Limitations of BMI

BMI does not directly measure body fat — it only looks at height and weight. This means the value can be high in athletes with high muscle mass, while older adults with muscle loss can have a "normal" BMI despite a high fat percentage. It also doesn't show where fat is distributed in the body; abdominal fat carries its own health significance and is assessed via waist circumference.

This calculator is designed for adults. In children and adolescents, BMI is interpreted using age- and sex-specific percentile curves. During pregnancy, pre-pregnancy BMI is used as the reference, and weight gain is monitored by a doctor.

How should you interpret your result?

BMI alone does not diagnose anything — it's a screening tool. If your value falls outside the normal range, it doesn't necessarily mean you have a health problem, but it's meaningful to have it assessed by a specialist together with values like waist circumference, blood sugar, blood pressure and cholesterol. Balanced nutrition, regular physical activity and adequate sleep support health at every BMI level.