BMI Calculator

Use this free online BMI calculator to check your Body Mass Index from your weight and height in seconds. Simply enter your weight in kilograms and height in centimeters to see which BMI category you fall into. This tool is for general informational purposes only and is not a substitute for professional medical advice.

How to Use the BMI Calculator

  1. Enter your weight in kilograms in the "Weight (kg)" field.
  2. Enter your height in centimeters in the "Height (cm)" field.
  3. Click "Calculate BMI" to view your BMI value and category instantly.

The BMI Formula

Body Mass Index compares your weight with your height. It is calculated as BMI = weight (kg) ÷ height (m)². Because most people in India know their height in centimetres or feet and inches, the calculator takes centimetres and divides by 100 to get metres before squaring. If you only know feet and inches, multiply total inches by 2.54 to get centimetres (5 ft 6 in = 66 in ≈ 167.6 cm).

Worked example: a person who weighs 70 kg and is 170 cm tall has a height of 1.70 m. 1.70 × 1.70 = 2.89, and 70 ÷ 2.89 = 24.22. The calculator shows a BMI of 24.22 and the category Normal.

BMI Categories: WHO and Indian Cut-offs

This calculator labels your result using the international WHO categories. Research has shown that South Asians tend to carry more body fat, particularly around the abdomen, at a given BMI than Europeans, and develop type 2 diabetes and heart disease at lower BMI values. For this reason, Indian consensus guidelines use lower cut-offs for adults.

CategoryWHO (used by this tool)Indian guidelines for adults
Underweight< 18.5< 18.5
Normal18.5 – 24.918.5 – 22.9
Overweight25 – 29.923 – 24.9
Obese30 and above25 and above

In the example above, a BMI of 24.22 is Normal on the WHO scale but falls in the Overweight band under the Indian cut-offs. If your result is between 23 and 25, it is worth paying attention to waist size, diet and activity even though the tool shows Normal.

Healthy Weight Range by Height

Rearranging the formula (weight = BMI × height²) gives the weight range that corresponds to a normal BMI at a given height:

HeightBMI 18.5 – 24.9BMI 18.5 – 22.9
160 cm47.4 – 63.7 kg47.4 – 58.6 kg
170 cm53.5 – 72.0 kg53.5 – 66.2 kg
180 cm59.9 – 80.7 kg59.9 – 74.2 kg

What BMI Does Not Tell You

  • It cannot tell muscle from fat. A gym-goer or athlete with a lot of muscle can show as overweight while having little body fat.
  • It ignores where fat is stored. Fat around the waist carries more health risk than fat on the hips and thighs, so a normal BMI with a large waist can still be a concern. Measuring your waist alongside BMI gives a better picture.
  • The adult categories do not apply to children and teenagers, whose BMI is judged against age- and sex-specific growth charts, or to pregnant women.
  • In older adults, loss of muscle and height with age can make BMI less reliable.

Use BMI as a quick screening number, not a diagnosis. A doctor can combine it with blood pressure, blood sugar, cholesterol and other checks to assess your actual health risk.

Frequently Asked Questions

BMI is calculated by dividing your weight in kilograms by the square of your height in meters (BMI = weight ÷ height²). This calculator converts your height from centimeters to meters automatically before applying the formula.

A BMI below 18.5 is classified as Underweight, 18.5-24.9 as Normal, 25-29.9 as Overweight, and 30 or above as Obese. These ranges are general population guidelines and may not apply to athletes, children, or pregnant women.

At the same BMI, South Asians on average have a higher percentage of body fat and more abdominal fat than many other populations, and their risk of diabetes and heart disease starts rising at lower BMI values. Indian guidelines therefore treat 23 – 24.9 as overweight and 25 or above as obese for adults.

No. BMI is a screening measure based only on weight and height. It does not measure body fat directly or account for muscle, bone or fat distribution. Consult a healthcare professional for a full assessment of your health.

The number itself is calculated the same way, but the adult categories shown here should not be used for children and teenagers. Their BMI has to be compared with growth charts for their age and sex, which a paediatrician can do.
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