Why India has its own BMI cutoffs
Two people can share a BMI of 24 and carry very different amounts of fat. That is the whole reason this calculator shows two verdicts for the same number. The WHO cutoffs were built mostly on data from European populations. In 2009 a consensus statement by Indian experts argued that Asian Indians tend to develop type 2 diabetes and heart-disease risk factors at lower BMI values and carry more fat around the abdomen at the same weight. Their guidance moved the "overweight" line down to 23 and the "obese" line to 25.
So a BMI of 24 is "normal range" on the WHO scale and "overweight" on the Asian-Indian scale. Neither is wrong. They answer slightly different questions: the WHO line is an international yardstick, while the Indian line is a more cautious screen for where metabolic risk starts to rise.
How the numbers are calculated
BMI is weight in kilograms divided by height in metres, squared. Feet, inches and pounds are converted first: one inch is 2.54 cm and one pound is 0.45359237 kg. The healthy range for your height runs the same formula backwards. Multiply the height in metres squared by 18.5 for the lower end, by 24.9 for the WHO upper end, and by 22.9 for the Asian-Indian upper end.
| BMI | WHO adult category | Asian-Indian category |
|---|---|---|
| Under 18.5 | Underweight | Underweight |
| 18.5 to 22.9 | Normal | Normal |
| 23.0 to 24.9 | Normal | Overweight |
| 25.0 to 29.9 | Overweight | Obese |
| 30.0 and above | Obese | Obese |
The category is decided on the BMI rounded to one decimal, which is the number you see on screen, so the label never disagrees with the figure.
A worked example: 70 kg at 170 cm
Height in metres is 1.70, and 1.70 squared is 2.89. Divide 70 by 2.89 and you get 24.2. On the WHO scale that sits in the normal range, a little under the 25 line. On the Asian-Indian scale it is overweight, because it is above 23.
The healthy range for 170 cm works out like this. Lower end: 18.5 x 2.89 = 53.5 kg. WHO upper end: 24.9 x 2.89 = 72.0 kg. Asian-Indian upper end: 22.9 x 2.89 = 66.2 kg. So the person at 70 kg is 2 kg under the WHO ceiling but about 3.8 kg over the Indian one.
Now add a waist. At 84 cm, the waist-to-height ratio is 84 / 170 = 0.49, under the 0.5 mark. That is a useful second opinion: the Indian-scale "overweight" label here is borderline rather than alarming, and the waist is not showing a clear fat-around-the-middle signal. If the waist were 95 cm instead, the ratio would be 0.56, and the same BMI would deserve more attention.
Why the optional waist field is worth filling in
Fat stored around the abdomen carries more metabolic risk than fat stored elsewhere, and BMI cannot tell the two apart. The waist-to-height ratio is simple: waist divided by height, both in the same unit. A commonly used rule of thumb is to keep the waist under half your height. Measure bare skin, halfway between the lowest rib and the top of the hip bone, after a normal breath out, tape level and snug but not pressing.
Common mistakes
- Mixing units. Entering pounds into the kg box gives a BMI more than double the real one. Use the unit switch rather than converting in your head.
- Entering 5.7 as five feet seven. 5.7 feet is 5 ft 8.4 in. Put 5 in the feet box and 7 in the inches box.
- Measuring the waist at the trouser line. Many people wear trousers below the navel, so the measured number comes out larger than the true waist.
- Treating one reading as a trend. Weight moves a kilo or two through the day with food and water. Weigh at the same time, ideally in the morning.
- Using the Indian cutoffs for a child. Under 18, BMI is read against age- and sex-specific growth charts.
What this calculator cannot tell you
BMI ignores muscle, so a regular gym-goer or an athlete can land in "overweight" with low body fat. It also ignores age: older adults can sit in the normal range while having lost muscle, and a slightly higher BMI is sometimes associated with better outcomes late in life. It does not adjust for pregnancy, and it says nothing about blood sugar, blood pressure or cholesterol, which are the things that actually matter for health. If your BMI is outside the normal range on either scale, or your waist ratio is above 0.5, treat that as a reason to look at those blood tests with your doctor, not as a verdict. If you want to track a goal, a trend over months is more telling than any single day. The age calculator can help you work out exactly how long it has been since a starting date.
Frequently asked questions
Which scale should I follow, WHO or Asian-Indian?
If you are of South Asian descent, the 23 and 25 cutoffs are the more cautious screen and are what many Indian doctors use. The WHO scale is better for comparing with international charts and research. Looking at both, as this page does, is reasonable.
Is a BMI of 23 to 24.9 dangerous?
No. It means the number has crossed the point where Indian guidance suggests paying closer attention to waist size, diet, activity and routine blood checks. It is a prompt to look, not a diagnosis.
Does the healthy weight range apply to everyone?
It applies to adults of average build. A very muscular or very small-framed person may be perfectly healthy a little outside it, and an older person may need a different target. Your doctor can interpret it for your situation.
Why does my waist ratio look fine but my BMI does not?
That usually points to muscle mass or a larger frame rather than excess fat. The reverse also happens: a normal BMI with a waist above half your height can mean fat is sitting around the middle, so it is worth taking seriously.