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What is BMI?
Body Mass Index (BMI) is a simple numerical measure of a person's body fat based on their weight and height. It is widely used by doctors and health professionals as a quick screening tool to classify adults as underweight, normal weight, overweight, or obese.
How to Use This BMI Calculator
- Enter your weight in kilograms (e.g., 70 kg).
- Enter your height in centimetres (e.g., 170 cm).
- Click Calculate to see your BMI and weight category.
BMI Formula
Example: 70 kg ÷ (1.70 m)² = 70 ÷ 2.89 = 24.2
BMI Categories
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Moderate risk of nutritional deficiency |
| 18.5 – 24.9 | Normal weight | Lowest health risk |
| 25.0 – 29.9 | Overweight | Increased risk |
| 30.0 and above | Obese | High risk of diabetes, heart disease |
BMI for South Asians
Research suggests that South Asians (including Indians) have a higher percentage of body fat at the same BMI compared to Caucasians. Many Indian health organisations recommend using lower cutoffs: overweight above 23, obese above 25 for the South Asian population.
How to Maintain a Healthy BMI
- Eat a balanced diet rich in vegetables, protein, and whole grains.
- Exercise at least 150 minutes per week (brisk walking, cycling, swimming).
- Limit processed foods, sugar, and refined carbohydrates.
- Stay hydrated — drink 2–3 litres of water daily.
- Get 7–8 hours of sleep per night, as poor sleep disrupts metabolism.
More Worked Examples
Here's how the same formula plays out at different heights and weights:
- 55 kg at 160 cm: 55 ÷ (1.60)² = 55 ÷ 2.56 = 21.5 (Normal weight)
- 85 kg at 175 cm: 85 ÷ (1.75)² = 85 ÷ 3.0625 = 27.8 (Overweight)
- 48 kg at 165 cm: 48 ÷ (1.65)² = 48 ÷ 2.7225 = 17.6 (Underweight)
Frequently Asked Questions
Is BMI accurate for everyone? No — it doesn't distinguish muscle from fat, so bodybuilders and athletes often show a "high" BMI despite low body fat. It also isn't designed for children, pregnant women, or the elderly.
What's a healthy BMI for Indians specifically? Because South Asians tend to carry more body fat at the same BMI as Europeans, many doctors in India treat 23–24.9 as "overweight" and 25+ as "obese" rather than the WHO's standard 25 and 30 cutoffs.
Who Should Use This Calculator
This BMI calculator is best suited for adults aged 18 and above who want a quick, general screening of their weight category. It works well for most desk-job professionals, homemakers, and moderately active adults tracking long-term weight trends. It is less reliable for pregnant or breastfeeding women (whose healthy weight gain follows separate trimester-wise charts), growing children and teenagers (who need age- and gender-specific growth charts, not adult BMI cutoffs), competitive athletes and bodybuilders with high muscle mass, and adults over 65, where a slightly higher BMI is sometimes protective rather than risky. The Indian Council of Medical Research (ICMR) and National Institute of Nutrition recommend using the lower South Asian cutoffs described above rather than the standard WHO figures for adults of Indian origin. If you fall into any of these excluded groups, ask your doctor which weight-assessment method is appropriate for you instead of relying on this general-purpose tool.
Frequently Asked Questions
Q: Is a BMI of 24-25 something to worry about right away?
A: Not necessarily. A BMI just above the "normal" cutoff is a signal to keep an eye on your diet and activity level, not an emergency. Doctors typically look at trends over months, along with waist circumference and family history of diabetes or heart disease, before recommending any intervention.
Q: Why do some Indian doctors use lower BMI cutoffs than the standard WHO chart?
A: Studies on South Asian populations have repeatedly shown higher body fat percentage and greater diabetes and heart disease risk at the same BMI compared with Western populations. This is why many Indian clinicians flag "overweight" from 23 and "obese" from 25, rather than the WHO's global 25 and 30 thresholds.
Q: Can I use this calculator to check my child's weight status?
A: No. Children and teenagers are still growing, so their healthy weight is judged against age- and sex-specific percentile growth charts, not the fixed adult BMI ranges used here. Ask your pediatrician for a growth-chart assessment instead.
Q: I work out regularly and my BMI still shows "overweight" — is that accurate?
A: Possibly not. BMI cannot distinguish muscle from fat, so muscular individuals — including many regular gym-goers and athletes — often score higher on the BMI scale despite having low body fat. Pairing this result with our Body Fat Calculator or a waist-to-height ratio gives a fuller picture.
Q: Should I make diet or medication decisions based on my BMI result alone?
A: No. This calculator is an educational screening tool, not a medical diagnosis. If your BMI falls outside the normal range, or you have existing health conditions, discuss a personalised plan with a doctor or registered dietitian rather than acting on this number alone.
Q: My BMI is normal, but I still have a large waist — should I be concerned?
A: Possibly, yes. A normal BMI with a high waist circumference (above roughly 90 cm for men or 80 cm for women, per commonly cited South Asian guidelines) can indicate visceral fat around the organs even when total body weight looks fine. This pattern, sometimes called "normal weight obesity" or being "TOFI" (thin outside, fat inside), still carries elevated metabolic risk, so pairing BMI with a simple tape-measure waist check gives a more complete picture.
BMI vs Waist-to-Height Ratio and Body Fat Percentage
BMI is popular because it only needs two numbers, but it isn't the only screening option available, and understanding how it compares to alternatives helps you interpret your result more sensibly. Waist-to-height ratio, calculated by dividing waist circumference by height, is increasingly favoured by researchers because it more directly reflects abdominal fat, the type most strongly linked to heart disease and type 2 diabetes risk in South Asian populations. A ratio above 0.5 is commonly flagged as a concern regardless of BMI category. Body fat percentage, whether estimated through our Body Fat Calculator or measured with skinfold calipers or bioelectrical impedance scales, goes a step further by separating fat mass from lean mass entirely, something BMI structurally cannot do. In practice, the three measures work best together: BMI as a quick first-pass screen, waist-to-height ratio as a check on abdominal fat distribution, and body fat percentage when you want the fullest picture of body composition, particularly if you strength train regularly or have a BMI that sits near a category boundary.
📅 Last reviewed: July 2026 · Formulas verified against RBI/SEBI/IT Dept guidelines.