BMI is a screening measure based on height and weight. It does not directly measure body fat or diagnose a health condition.
What is BMI?
Body Mass Index (BMI) is a value calculated from a person's weight and height. It is commonly used as an initial screening measure for weight categories in adults. BMI is only one part of a health assessment and should be interpreted alongside other information, such as body composition, medical history, and clinical measurements.
How to calculate BMI
For metric measurements, divide weight in kilograms by height in metres squared.
Example: If someone weighs 70 kg and is 170 cm tall, their height is 1.70 m. BMI = 70 ÷ (1.70 × 1.70) = 24.2 kg/m² (rounded to one decimal place).
For imperial measurements, BMI can be calculated as 703 × weight in pounds ÷ height in inches squared. This calculator converts the entered values to metric units before calculating.
Adult BMI categories: WHO and Asian-Indian references
Different references use different thresholds. The table below is a simplified adult screening comparison. It is not a diagnosis and may not be appropriate for every person.
| Category | WHO international reference | Asian-Indian reference |
|---|---|---|
| Underweight | Below 18.5 | Below 18.5 |
| Normal range | 18.5–24.9 | 18.5–22.9 |
| Overweight | 25.0–29.9 | 23.0–24.9 |
| Obesity | 30.0 or above | 25.0 or above |
Asian-Indian thresholds are lower because metabolic risk can occur at lower BMI levels in South Asian populations. These categories are screening references; a healthcare professional can interpret them in context.
Healthy-weight range estimate
For the height you enter, this calculator shows the weight range corresponding to BMI 18.5 through 22.9. The range is a mathematical reference rather than a personal goal. Age, muscle mass, pregnancy, health conditions, and other factors can affect what is appropriate for an individual.
What BMI cannot tell you
- It cannot distinguish muscle from fat or measure body-fat percentage directly.
- It does not show where body fat is distributed.
- It does not diagnose diabetes, heart disease, or another medical condition.
- It needs different interpretation for children and teenagers; adult thresholds should not be used for them.
- It may be less informative for some athletes, older adults, pregnant people, and people with certain health conditions.
Frequently asked questions
What is a normal BMI for adults?
Under the WHO international adult reference, 18.5 to below 25 is the normal-weight category. The Asian-Indian reference commonly uses 18.5 to below 23. These are screening ranges, not a complete measure of health.
Is BMI calculated differently for men and women?
The standard adult BMI formula is the same for men and women. BMI does not account for all differences in body composition, so the result should be interpreted in context.
Can I use this BMI calculator for a child?
This tool displays adult reference categories. Children and teenagers need BMI-for-age assessment using age- and sex-specific growth charts, ideally with guidance from a healthcare professional.
Does BMI tell me how much weight I should lose?
No. BMI and a calculated weight range cannot determine an individual weight-loss target. Discuss personal goals with a qualified healthcare professional, especially if you have a medical condition or concerns about your weight.
Are my measurements saved?
This page's calculator logic runs in your browser and does not send the measurement fields to the server. Your browser, extensions, or other site services may have their own behaviour, so avoid entering information you do not want processed.
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Health disclaimer: This calculator is for general educational information only. It is not a medical diagnosis or a substitute for professional advice, diagnosis, or treatment. If you have health concerns, speak with a qualified healthcare professional.