How to use the BMI Calculator
- Enter your height in centimetres. If you know it in feet and inches, convert it first: 1 foot is 30.48 cm and 1 inch is 2.54 cm.
- Enter your weight in kilograms.
- Read your BMI, your category and the normal weight range for your height.
Formula used
BMI = weight (kg) ÷ height (m)². WHO adult categories: below 18.5 underweight, 18.5 to 24.9 normal, 25 to 29.9 overweight, 30 and above obese.
Worked example
Here is the BMI Calculator worked through with the example values shown above, so you can check each step by hand.
| Inputs | |
|---|---|
| Height | 170 cm |
| Weight | 65 kg |
| Result | |
| Your BMI | 22.49 |
| Category (WHO) | Normal weight |
| Normal weight range for your height | 53.5 – 72.0 kg |
How BMI is calculated
BMI = weight in kg ÷ (height in metres)². A person who weighs 65 kg and is 170 cm tall has a BMI of 65 ÷ (1.70 × 1.70) = 22.5, which falls in the normal range. For that height, a BMI between 18.5 and 24.9 corresponds to a weight of about 53.5 kg to 72.0 kg.
The same weight can mean different things at different heights. Someone who is 160 cm and 80 kg has a BMI of 31.3, while someone who is 180 cm and 70 kg has a BMI of 21.6.
WHO categories and the Indian context
The World Health Organization classes adult BMI as underweight below 18.5, normal from 18.5 to 24.9, overweight from 25 to 29.9 and obese at 30 and above. This calculator uses those standard cut-offs.
Research has shown that people of South Asian origin can carry more body fat and face higher metabolic risk at a lower BMI. Indian consensus guidelines therefore use lower cut-offs, treating a BMI from 23 as overweight and from 25 as obese. If you are of South Asian origin, ask your doctor which thresholds suit you.
What BMI cannot tell you
BMI does not separate muscle from fat or show where fat is stored, so a muscular athlete can have a high BMI while being healthy. It can also underestimate risk in older adults who have lost muscle. Waist circumference, blood tests, activity levels and family history give a fuller picture.
This calculator is not for children and teenagers, who are assessed using age-and-sex-specific growth charts, and it is not suitable during pregnancy. Treat the result as information only and speak to a doctor or dietitian before making health decisions.
Frequently asked questions
What is a healthy BMI?
The WHO defines a normal adult BMI as 18.5 to 24.9. Some guidelines for South Asian adults use a lower upper limit, so ask your doctor which range applies to you.
How do I calculate BMI?
Divide your weight in kilograms by your height in metres squared. For 65 kg and 170 cm, BMI = 65 ÷ 2.89 = 22.5.
Is BMI accurate?
It is a simple screening tool and not a measure of body fat. Athletes, older adults and people with unusual body composition can be misclassified.
What weight is normal for my height?
The calculator shows the weight range that gives a BMI between 18.5 and 24.9 for your height. At 170 cm that range is about 53.5 kg to 72.0 kg.
Can children use this BMI calculator?
No. Children and teenagers are assessed with BMI-for-age growth charts. Speak to a paediatrician for guidance.
Should I rely on BMI to decide on a diet or exercise plan?
Use it only as a first indicator. A doctor or qualified dietitian can look at your overall health, and they will give you advice that is right for you.
This calculator gives estimates for information only. Actual figures from a bank, employer, tax authority or doctor may differ. It is not financial, tax, legal or medical advice.