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Body Mass Index

BMI Calculator — Find Your Body Mass Index & Healthy Weight Range

Calculate your Body Mass Index from height and weight, see your WHO weight category, and get your healthy weight range in kg. Includes the lower Asian/Indian BMI cut-offs used by doctors across South Asia.

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Formula: BMI = Weight (kg) ÷ Height (m)²
Imperial: BMI = 703 × Weight (lb) ÷ Height (in)²

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Disclaimer: Health metrics provided by this tool are for general informational purposes only and should never replace professional medical advice, diagnosis, or treatment. BMI is a screening measure, not a diagnosis — consult a doctor for a complete assessment of your health, especially if you are an athlete, pregnant, elderly, or have a medical condition affecting body composition.

How BMI Is Calculated

The Formula: Body Mass Index divides your weight by the square of your height, giving a single number used to screen for weight categories that may lead to health problems:

BMI = Weight (kg) ÷ Height (m)²

Where:

In imperial units: BMI = 703 × Weight (lb) ÷ Height (in)²

Step-by-Step Worked Example

Let's say you weigh 70 kg and are 170 cm (1.70 m) tall.

  1. Step 1: Convert height to metres: 170 cm ÷ 100 = 1.70 m
  2. Step 2: Square the height: 1.70² = 2.89
  3. Step 3: Divide weight by that number: 70 ÷ 2.89 = 24.22
  4. Result: BMI = 24.2 — this falls in the "Normal" category under WHO's standard classification (18.5–24.9)

The healthy weight range for someone 170cm tall is approximately 53.5 kg to 72.0 kg under the standard WHO range, or roughly 53.5 kg to 66.2 kg under the tighter Asian/Indian guideline (BMI 18.5–22.9).

WHO BMI Classification

CategoryStandard WHO BMIAsian/Indian BMI
UnderweightBelow 18.5Below 18.5
Normal weight18.5 – 24.918.5 – 22.9
Overweight25.0 – 29.923.0 – 24.9
Obese Class I30.0 – 34.925.0 – 29.9
Obese Class II35.0 – 39.930.0+
Obese Class III40.0 and above—

India's health guidelines (and WHO's own Asian BMI advisory) use lower cut-offs because South Asians tend to carry more visceral (abdominal) fat and face higher diabetes and cardiovascular risk at the same BMI as Western populations. Many Indian doctors flag "overweight" starting at BMI 23 rather than 25.

Frequently Asked Questions

Body Mass Index (BMI) is a screening measure calculated as weight in kilograms divided by height in metres squared: BMI = Weight (kg) ÷ Height (m)². In imperial units, BMI = 703 × Weight (lb) ÷ Height (in)². It's a quick, low-cost way to estimate whether someone is underweight, normal weight, overweight, or obese at a population level.
Yes. The standard WHO classification treats BMI 18.5-24.9 as normal and 25+ as overweight. However, WHO's Asian BMI guidelines (used across India and much of South Asia) lower the overweight cut-off to 23 and the obese cut-off to 25, because South Asians tend to develop diabetes and cardiovascular risk at lower BMI values than Western populations, largely due to higher body fat percentage at the same BMI.
BMI doesn't distinguish between muscle mass and fat mass, so muscular individuals (athletes, bodybuilders) are often misclassified as overweight or obese despite low body fat. It also doesn't account for fat distribution — visceral (abdominal) fat carries more health risk than fat elsewhere, which is why doctors often combine BMI with waist circumference. BMI ranges also differ for children, older adults, and pregnant women, and this calculator is designed for adults.
Your healthy weight range is the weight at which your BMI falls between 18.5 and 24.9 (or 18.5-22.9 under Asian guidelines). This calculator computes both bounds automatically from your height — for example, at 170cm the standard healthy range is approximately 53.5 kg to 72.0 kg.
The classic BMI formula doesn't factor in muscle mass, gender, or age directly — it's a simple weight-to-height ratio. For a more complete picture, combine BMI with waist circumference, body fat percentage, and — for older adults — muscle mass tracking, since BMI alone can under-flag health risk in older adults who've lost muscle but kept a "normal" BMI (sometimes called normal-weight obesity).