What BMI actually is
Body Mass Index is your weight in kilograms divided by your height in metres squared. That is the whole thing. It was devised in the 1830s as a way of describing populations, not individuals, and it has been doing a job it was never designed for ever since.
That does not make it useless. As a quick screening number it is genuinely informative at the extremes, it costs nothing, and it needs no equipment. It simply cannot tell you whether you are healthy.
BMI categories
The familiar thresholds are the WHO's. India uses lower ones, and if you are of South Asian descent the Indian column is the more relevant of the two.
| Category | WHO | India |
|---|---|---|
| Underweight | Below 18.5 | Below 18.5 |
| Normal | 18.5 – 24.9 | 18.5 – 22.9 |
| Overweight | 25.0 – 29.9 | 23.0 – 24.9 |
| Obese | 30.0 and above | 25.0 and above |
Why the Indian thresholds are lower
Research across South Asian populations found that people of Indian descent tend to carry a higher proportion of body fat — and more of it around the abdomen — at any given BMI than European populations do. The health risks associated with a BMI of 25 in Europe show up closer to 23 here.
Practically, this means a woman reading 24 should not take the WHO's "normal" as reassurance. It is worth paying attention somewhat earlier.
What BMI misses
It cannot tell muscle from fat
Muscle is denser than fat. Two women of identical height and weight — one sedentary, one training three times a week — have the same BMI and quite different bodies. If you have been lifting for a while, expect BMI to overstate your situation.
It ignores where fat sits
Fat around the abdomen carries considerably more health risk than fat on the hips and thighs. BMI cannot see this at all, which is why waist circumference is often the more useful number. For Indian women, a waist above roughly 80cm is the commonly cited threshold for increased risk.
It was not built for everyone
BMI is unreliable during pregnancy, for anyone under 18, for older adults losing muscle mass, and for athletes. If any of those describe you, treat the result as close to meaningless.
Better numbers to watch
- Waist measurement — a single tape measure tells you more about abdominal fat than BMI ever will.
- Waist-to-height ratio — keeping your waist under half your height is a simple, surprisingly robust guide.
- How your clothes fit — unglamorous, and it picks up body composition changes the scale misses entirely.
- What you can do — stairs without stopping, carrying shopping, sleeping well. This is what fitness actually buys you.
If your BMI is higher than you'd like
The instinct is to do something drastic. Drastic approaches produce fast initial results and almost always unwind, usually with a little extra on top.
What works is dull: walk more, snack less, keep portions sensible, prioritise protein, sleep properly. Around half a kilo a week is a realistic rate — slow enough to feel unimpressive, fast enough to be twelve kilos in six months.
If you want help staying consistent, the weight loss tracker scores those exact behaviours daily, and the 20-minute beginner home workout needs no gym and no equipment.
Frequently asked questions
What is a healthy BMI for a woman?
By the global WHO standard, 18.5 to 24.9 is classed as normal. Indian health guidelines use lower thresholds, treating 18.5 to 22.9 as normal and 23 and above as overweight, because South Asians tend to carry more body fat and more abdominal fat at the same BMI.
Is BMI different for men and women?
The formula is identical. Interpretation differs in practice, because women naturally carry a higher percentage of body fat than men at the same BMI. This is one of several reasons BMI should be treated as a rough screening number rather than a measure of health.
Why does India use a lower BMI cut-off?
Research found that Indians and other South Asians develop higher body fat, more abdominal fat and greater risk of type 2 diabetes and heart disease at lower BMI values than European populations. Indian guidelines therefore set the overweight threshold at 23 rather than 25.
Is BMI accurate if I lift weights?
No. BMI cannot distinguish muscle from fat, so anyone with significant muscle mass will read higher than their actual body fat justifies. If you train regularly with weights, waist measurement and how your clothes fit tell you considerably more.
How often should I check my BMI?
Once a month at most. BMI changes slowly, and checking more often simply picks up normal fluctuations in water weight. Tracking your weight trend over weeks is far more informative than any single BMI reading.
What should I do if my BMI is high?
Do not panic, and do not start an extreme diet. The most reliable approach is small sustainable changes: walk more, cut back on snacking, moderate your portions and get enough sleep. A loss of around half a kilo per week is sensible. If your BMI is in the obese range or you have other symptoms, see a doctor.
Medical disclaimer: this calculator gives a general estimate using standard population formulas. It is not medical advice and cannot account for your individual health, medication or body composition. Please speak to a qualified doctor or registered dietitian before making significant changes — especially if you are pregnant, breastfeeding, under 18, or managing a health condition. See the full disclaimer.