BMI Calculator
Check your Body Mass Index and see which weight category you fall into.
BMI ranges
Underweight: below 18.5 • Normal: 18.5–24.9 • Overweight: 25–29.9 • Obese: 30+
What is BMI, and who needs a BMI calculator?
Body Mass Index (BMI) is a single number that compares your weight with your height. It is a quick screening tool that places adults in one of four groups: underweight, normal weight, overweight or obese. Enter your height and weight in metric or imperial units, and this calculator shows your BMI and category instantly.
People use it before starting a fitness plan, while tracking weight loss or gain, during a routine health check, or when filling in forms for gyms, insurance and some job medicals. With lifestyle-related health problems rising across India, a quick BMI check is a simple first step before talking to a doctor or dietitian.
Formula used
- Metric: BMI = weight (kg) ÷ height (m)²
- Imperial: BMI = 703 × weight (lb) ÷ height (in)²
In metric mode, height in centimetres is first divided by 100 to get metres. In imperial mode, feet are converted to inches (1 ft = 12 in) and added to any extra inches. The result is compared with these ranges: underweight below 18.5, normal 18.5 to 24.9, overweight 25 to 29.9, and obese 30 and above.
Worked example
Consider an adult who is 170 cm tall and weighs 65 kg.
- Height in metres = 170 ÷ 100 = 1.70
- Height squared = 1.70 × 1.70 = 2.89
- BMI = 65 ÷ 2.89 = 22.5
A BMI of 22.5 falls in the normal weight range. At the same height, weights from about 53.5 kg (18.5 × 2.89) to about 72 kg (24.9 × 2.89) keep BMI in the normal range.
Imperial example: 5 ft 7 in and 143 lb. Height = 5 × 12 + 7 = 67 in. BMI = 703 × 143 ÷ (67 × 67) = 100,529 ÷ 4,489 = 22.4. For comparison, someone 160 cm tall weighing 78 kg has a BMI of 78 ÷ 2.56 = 30.5, which this calculator labels obese.
Frequently asked questions
What is a healthy BMI for Indians?
The standard WHO range for a normal BMI is 18.5 to 24.9, and this calculator uses it. Several Indian health guidelines treat 23 and above as overweight and 25 and above as obese, because South Asians tend to carry more body fat at a lower BMI.
Is BMI different for men and women?
No. The formula and the adult ranges are the same for both. BMI does not consider sex, age or body build, so women and men with the same height and weight get the same number.
Can I use this BMI calculator for children and teenagers?
No. For anyone under 18, BMI is judged against age and sex based growth charts, not the adult ranges. Please ask a paediatrician to interpret a child's result.
Why does BMI look wrong for athletes and gym-goers?
Muscle is denser than fat, so a muscular person can show a high BMI despite low body fat. In such cases waist size and body fat percentage give a better picture.
How does the imperial option work?
Your height in feet and inches is converted to total inches, for example 5 ft 7 in is 67 in. BMI is then 703 times your weight in pounds, divided by height in inches squared.
Limitations and accuracy
BMI is a screening number, not a diagnosis. It does not measure body fat, muscle, bone density or where fat sits on your body, so a waist measurement and blood tests tell you more. This calculator applies the standard WHO categories to every adult, which may understate health risk for many Indians. It is also not designed for children, pregnant women or older adults who have lost muscle. Speak to a doctor before making major diet or exercise changes.