BMI Calculator - Check Your Body Mass Index
Use our free online BMI Calculator to instantly check your Body Mass Index. By entering your weight and height, you can determine if you have a healthy body weight for your height according to World Health Organization (WHO) guidelines.
What is BMI (Body Mass Index)?
The Body Mass Index (BMI) is a simple mathematical calculation used to estimate body fat based on an individual's weight and height. It is widely used by doctors, health professionals, and fitness experts as a quick screening tool to identify possible weight problems for adults.
BMI Calculation Formula
The formula for BMI is weight in kilograms divided by height in meters squared. Since most people measure height in centimeters, our calculator converts it for you automatically.
How to Calculate Your BMI Manually
Let's look at an example of calculating BMI if a person weighs 68 kg and is 165 cm (1.65 meters) tall.
165 cm ÷ 100 = 1.65 m
Step 2: Square the Height
1.65 × 1.65 = 2.7225
Step 3: Divide Weight by Squared Height
68 ÷ 2.7225 = 24.98
Answer: The BMI is 24.98 (Normal Weight).
BMI Categories (WHO Guidelines)
According to the World Health Organization, the standard BMI categories for adults (men and women) are:
- Underweight: BMI less than 18.5
- Normal Weight: BMI between 18.5 and 24.9
- Overweight: BMI between 25.0 and 29.9
- Obesity: BMI 30.0 or higher
What this tool does
Calculate body mass index from height and weight as a quick screening measure. The result is a simple mathematical estimate and should not be treated as a diagnosis or a complete assessment of health.
How it works
The calculator divides weight in kilograms by height in metres squared, or converts the supplied units before applying the same formula. Rounding is used only for display.
Worked example
A person weighing 70 kg and measuring 1.75 m receives a BMI of about 22.9. The number is a screening result, not a description of body composition or fitness.
Practical uses
Use it for learning the formula, checking a rough figure, or preparing questions for a qualified health professional. Record the units carefully and compare results over time only in a consistent way.
Limits and privacy
BMI can be misleading for children, pregnancy, older adults, athletes, and people with unusual muscle or fluid distribution. It does not diagnose illness; seek professional advice for personal health decisions.
Frequently Asked Questions
Is BMI accurate for everyone?
BMI is a great general indicator, but it does not distinguish between muscle and fat. For example, athletes and bodybuilders might have a high BMI due to muscle mass, not excess fat. It is also not always accurate for pregnant women or the elderly.
Does BMI change with age or gender?
For adults (ages 20 and older), BMI is interpreted the same way for both men and women of all ages. However, for children and teens, BMI is age and gender-specific.
What should I do if my BMI is too high?
If your BMI falls into the overweight or obese category, it is recommended to consult with a healthcare provider or a registered dietitian. They can evaluate your overall health and suggest lifestyle, diet, or exercise changes.