BMI Calculator
Calculate your Body Mass Index instantly. Get your BMI category, healthy weight range, and personalised health insights — in metric or imperial units.
What is BMI?
BMI (Body Mass Index) = Weight (kg) ÷ Height² (m²)
BMI is a simple number that classifies your body weight relative to your height. It is widely used as a screening tool to identify whether a person is underweight, normal weight, overweight, or obese.
BMI Categories (WHO standard):
Below 18.5 = Underweight · 18.5–24.9 = Normal weight · 25–29.9 = Overweight · 30–34.9 = Obese Class I · 35–39.9 = Obese Class II · 40+ = Obese Class III
Important note: BMI is a screening tool, not a diagnostic one. Athletes with high muscle mass may have a high BMI without excess fat. Always consult a healthcare professional for a complete health assessment.
How to read your BMI — the complete guide
How BMI is calculated
Body Mass Index is your weight in kilograms divided by your height in metres squared: BMI = weight (kg) ÷ height (m)². It's a quick screening number that estimates whether your weight is in a healthy range for your height — it needs no equipment beyond a scale and a measuring tape, which is why doctors and health surveys have used it for decades.
The standard WHO categories
The World Health Organization's international BMI bands are the ones most calculators show:
| Category | BMI range (kg/m²) |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese | 30.0 and above |
BMI was never meant to judge an individual — it was devised in the 1830s as a way to describe populations, and only later became a clinical shorthand. That history explains both its usefulness and its limits: it's excellent for spotting trends across large groups quickly and cheaply, but blunt when applied to one person, because it knows nothing about your muscle, bone, or where your body stores fat. Treat the category it gives you as a flag worth investigating, not a final answer.
Why India uses lower cut-offs (the part most calculators miss)
If you're in India, the WHO scale can understate your risk. Research consistently shows that Asian-Indian bodies tend to carry more body fat — and more of it around the abdomen — at the same BMI as Western populations, and develop type-2 diabetes and heart disease at lower BMI values. Because of this, Indian medical guidelines use tighter thresholds than the global standard:
| Category (Asian-Indian) | BMI range (kg/m²) |
|---|---|
| Normal | 18.5 – 22.9 |
| Overweight / at-risk | 23.0 – 24.9 |
| Obese | 25.0 and above |
In practice this means a BMI of 24 — comfortably "normal" by WHO numbers — is already in the overweight range for Indians. The 2024 revised Indian obesity guidelines go further, combining BMI above 23 with waist circumference (a practical warning line is roughly 90 cm for men and 80 cm for women) to judge abdominal obesity, which is a stronger predictor of metabolic risk than BMI alone.
Who should use a BMI check, and when
- Adults tracking general health who want a fast, free indicator between doctor visits.
- Anyone in India who wants to see their number against the stricter Indian cut-offs, not just the WHO scale.
- People preparing for a check-up who want context before discussing weight and metabolic health with a doctor.
What BMI cannot tell you — read this before acting on a number
BMI is a screening estimate, not a diagnosis, and it has real blind spots:
- It can't tell muscle from fat. Muscular athletes often score "overweight" or "obese" despite low body fat, because muscle is dense.
- It ignores where fat sits. Two people with the same BMI can have very different health risks depending on abdominal fat — which is why waist measurement matters.
- It's not designed for everyone. BMI is unreliable for children and teens (who use age-and-sex growth charts), pregnant women, the elderly, and people with certain medical conditions.
- It's a starting point, not a verdict. A single number can't capture fitness, diet, blood pressure, or blood sugar.
Frequently asked questions
What is a healthy BMI for Indians?
By Indian guidelines, the normal range is 18.5 to 22.9. Overweight begins at 23 and obesity at 25 — lower than the WHO thresholds of 25 and 30 — because Indians face higher metabolic risk at lower BMI values.
Why is my BMI "overweight" when I feel fit?
BMI can't distinguish muscle from fat, so people with high muscle mass, such as athletes and regular strength trainers, often score higher than their actual body fat warrants. Body-fat percentage and waist measurement give a fuller picture.
Is BMI accurate for older adults?
Less so. Muscle mass declines and body composition shifts with age, so standard BMI bands can misjudge health risk in older adults. It's best interpreted alongside other measures and a doctor's input.
Should I use BMI for my child?
No — children and teenagers are assessed with age- and sex-specific BMI-for-age growth percentiles, not the adult bands. Adult BMI categories don't apply to them.
What matters more than BMI?
For metabolic risk, waist circumference and the ratio of waist to height are often more telling, because abdominal fat is more strongly linked to diabetes and heart disease than overall weight.