Understanding your
BMI result

What BMI is and how it is calculated

Body mass index (BMI) compares your weight with your height in a single number. It is a simple, widely used first check, which is why doctors, fitness apps and health forms all ask for it.

1. 1Convert your height to metres.
2. 2Multiply that number by itself.
3. 3Divide your weight in kilograms by the result.
4. 4Round to one decimal place.

The adult categories are the same for men and women. Because BMI needs only a weighing scale and a tape measure, it is easy to track at home, which is also why it is a blunt instrument.

BMI categories: the standard chart

The World Health Organization's standard categories for adults are in the table below. They do not apply to children and teenagers, whose BMI is read against age- and sex-specific growth charts.

For a person 1.75 m tall, the normal range of 18.5 to 24.9 works out to roughly 56.7 kg to 76.3 kg. At 70 kg and a BMI of 22.9, the example above sits comfortably inside it.

The categories are bands, not cliffs. A BMI of 24.8 and one of 25.1 describe almost the same person, so the trend over time and your overall health matter more than which side of a line you land on. A low BMI deserves attention too: being underweight can point to poor nutrition or an underlying illness, so it is worth raising with a doctor.

Why Indian and Asian cut-offs are lower

Many Indian and Asian guidelines use lower cut-offs than the standard chart, because health risks can begin to rise at lower BMI values in many Asian populations. You will often see 23 used instead of 25 for overweight, and 27.5 instead of 30 for higher risk. Exact thresholds differ between guidelines, so ask your doctor which one they follow.

With the lower cut-off, the 70 kg example is just under the line: at 1.75 m, a BMI of 23 is reached at about 70.4 kg.

The formula does not change; only the way the result is read does. The same BMI can fall in the normal band on one chart and the overweight band on another, so find out which chart a report, app or doctor is using before you compare numbers.

What BMI cannot tell you

BMI uses only two measurements, so it misses a lot. It is a screening tool, not a diagnosis.

• Muscle and fat. Muscle is dense, so a muscular person or athlete can have a high BMI with little body fat.
• Where fat sits. BMI does not show body fat distribution. Waist measurement adds useful information.
• Age. Older adults tend to lose muscle, so the same BMI can mean more body fat than in a younger adult.
• Growth and pregnancy. Children, teenagers and pregnant women need different reference methods.
• A single reading. Weight moves through the day with food and water. To compare readings over time, weigh yourself under similar conditions, such as the same time of day in light clothing.

What to do with your result

If your BMI falls outside the normal range, or you are unsure how to read it, talk to a doctor or a registered dietitian. They will usually look at waist size, blood tests, family history and lifestyle alongside BMI. Avoid big changes to eating or exercise based on a single number.

Questions worth asking at an appointment:

• Is BMI a good guide for my build and activity level?
• Should we also check my waist size or run blood tests?
• Which BMI cut-offs do you use for Indian adults?

BMI also says nothing about how much energy you use each day. To estimate that, use the TDEE Calculator, then discuss any change to your diet with a professional.