How to Calculate Your BMI (and What It Doesn't Tell You)
At a health check-up, the nurse writes a number next to "BMI" and moves on. Online, the number gets thrown around as if it were a verdict. It isn't. It's a quick screening ratio of weight to height, useful for spotting trends and starting a conversation with a doctor. BMI calculator works it out and shows where it falls on the World Health Organization's adult chart, alongside the lower cut-offs used for Asian populations.
Steps
- Choose kilograms or pounds.
- Enter height (centimetres, or feet and inches) and weight.
- Read your BMI, to one decimal place, and its band.
The formula
BMI = weight in kilograms ÷ (height in metres)². Imperial values are converted to kilograms and metres first. Someone 175 cm tall weighing 70 kg has a BMI of 70 ÷ 1.75² = 22.9.
The bands
WHO adult bands:
| BMI | Band |
|---|---|
| Under 18.5 | Underweight |
| 18.5–24.9 | Healthy |
| 25–29.9 | Overweight |
| 30 or more | Obese |
Asian cut-offs: WHO Asia-Pacific guidance, also used in India, treats 23–24.9 as overweight and 25 or more as obese, because health risks such as type 2 diabetes rise at lower BMIs in Asian populations. The page shows both so you can read the one your doctor uses.
That 22.9 example is healthy on both scales. At 24, it's healthy on the WHO chart but overweight on the Asian one, which is a real difference for millions of people in India and elsewhere in Asia.
BMI Prime
The page also shows BMI Prime: your BMI divided by 25, the top of the WHO healthy range. Under 1.0 means you're below that limit; 1.2 means 20% above it. It's a convenient way to say "how far from the line" in one number.
What BMI gets wrong
BMI doesn't know what your weight is made of. It can mislead for:
- Athletes and very muscular people, who can read as overweight while being very fit.
- Older adults, who may have lost muscle and read as healthy despite carrying more fat.
- Children and teenagers, who need age- and sex-specific growth charts, not adult bands.
- Pregnancy, when the adult bands simply don't apply.
The page doesn't estimate body fat. Waist measurement is a useful companion: fat around the middle carries more risk than the same weight elsewhere, and a tape measure costs almost nothing.
Using the number well
- Track the trend, not one reading. Weigh at the same time of day, every few weeks.
- Pair it with waist size, blood pressure and blood tests from your check-ups.
- Talk to a doctor about what the number means for you, especially if it's changed quickly or sits near a cut-off.
Rules as of October 2026
Rules as of 27 October 2026. The page uses the WHO adult BMI bands and shows the lower Asian cut-offs alongside. BMI is a screening number, not a diagnosis. Talk to a doctor about what your number means for you.
Official sources:
Privacy
The page says your height and weight stay in the tab, aren't uploaded and aren't stored, and states plainly that it's not medical advice. Google ads appear on the page, as across the site.
FAQ
Is a "healthy" band a clean bill of health? No. It's only where the number sits on the chart.
Why are Asian cut-offs shown? Health risks rise at lower BMI in Asian populations, so WHO Asia-Pacific guidance uses 23 and 25.
What is BMI Prime? BMI divided by 25; 1.0 is the top of the healthy range.
Does it store my result? No.
Check your number, then discuss it with your doctor: BMI calculator.
— Alok Kumar Singh