Body Mass Index (BMI) Calculator
Understand your health better with our smart BMI Calculator. Instantly find your BMI score and see where you stand — healthy, overweight, or underweight.
Healthy weight for your height: —
Standard WHO ranges. Updates as you type — not a substitute for medical advice.
What is BMI?
Body Mass Index (BMI) is a numerical value calculated from your weight and height. It provides a simple measure to evaluate whether you have a healthy body weight for your height.
How BMI is Calculated
The formula for BMI is:
BMI Categories
| BMI Range | Weight Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Higher risk for health problems |
| 18.5 – 24.9 | Normal weight | Lower risk for health problems |
| 25 – 29.9 | Overweight | Increased risk for health problems |
| 30 and above | Obese | High risk for health problems |
Why BMI Matters
Having a BMI in the overweight or obese range increases your risk for:
- Heart disease and stroke
- Type 2 diabetes
- Certain types of cancer
- Sleep apnea and breathing problems
- Osteoarthritis
- Mental health issues like depression
BMI Calculator: Check Your Body Mass Index Instantly
Body Mass Index (BMI) is a simple, widely used screening number that estimates whether your weight is in a healthy range for your height. Our BMI calculator does the maths for you in seconds: just enter your height and weight, and it returns your BMI along with the category it falls into. BMI is popular because it is quick, free, and needs no special equipment, which is why doctors, gyms, and health surveys use it as a first-glance indicator.
It is important to remember that BMI is a starting point, not a diagnosis. It gives you a useful signal about your weight, but it does not capture the full picture of your health. Think of it as one reading among many, alongside your waist measurement, blood pressure, blood sugar, activity levels, and how you feel day to day.
How BMI Is Calculated
The metric formula is straightforward:
BMI = weight (kg) ÷ [height (m)]²
For example, someone weighing 68 kg at 1.70 m has a BMI of 68 ÷ (1.70 × 1.70) = 68 ÷ 2.89 = 23.5.
If you prefer imperial units, the formula uses a conversion factor of 703:
BMI = [weight (lb) ÷ height (in)²] × 703
You do not need to memorise either version. Enter your numbers in whichever units are comfortable and the calculator handles the conversion automatically. The result is the same BMI value regardless of which formula is used.
BMI Categories and What They Mean
The World Health Organization (WHO) groups BMI into the standard categories below. These ranges apply to most adults aged 20 and over.
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal (healthy) weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obese |
A higher BMI is linked at a population level to greater risk of conditions such as type 2 diabetes, heart disease, and high blood pressure, while a very low BMI can signal undernutrition or other concerns. These are statistical associations, not certainties for any one person, so try not to read a single number as a verdict on your health.
BMI Cut-offs for Indians and South Asians
Research shows that people of South Asian descent, including Indians, tend to carry more body fat and face higher risks of diabetes and heart disease at a lower BMI than the standard WHO thresholds suggest. Because of this, several Indian and Asian-Pacific guidelines use lower cut-offs:
| BMI Range | Category (Asian/Indian guideline) |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 22.9 | Normal (healthy) weight |
| 23.0 – 24.9 | Overweight (at-risk) |
| 25.0 and above | Obese |
If you are of Indian or South Asian background, it is worth interpreting your result against these lower thresholds. Many clinicians in India also pay close attention to waist circumference, since abdominal fat is a particularly strong risk marker in this population.
The Limits of BMI
BMI is handy but blunt. It uses only height and weight, so it cannot tell muscle from fat. A trained athlete with heavy muscle may register as overweight despite being very lean, while someone with low muscle mass may have a normal BMI yet carry excess fat. BMI also does not show where fat sits on the body, which matters because fat around the abdomen is more harmful than fat on the hips or thighs.
BMI is also a poor fit for certain groups. It is not reliable for children and teenagers, who need age- and sex-specific growth charts; for older adults, whose muscle mass and height change with age; or for pregnant women, whose weight gain is expected and healthy. For these groups, BMI should be set aside in favour of more appropriate measures.
The bottom line: use your BMI as a friendly nudge to think about your health, not as the final word. If your result concerns you, or if you are planning major changes to your diet, exercise, or weight, speak with a doctor or qualified dietitian who can assess you as a whole person and give advice tailored to you.
Frequently Asked Questions
For most adults, a BMI between 18.5 and 24.9 is considered the healthy or normal range under WHO guidelines. Below 18.5 is classed as underweight, 25 to 29.9 as overweight, and 30 or above as obese. These are general ranges, so your doctor may interpret them in the context of your age, build, and overall health.
BMI is a reliable screening tool for populations but only a rough guide for individuals. Because it uses just height and weight, it cannot distinguish muscle from fat or show where fat is stored. Athletes, people with high muscle mass, and others may get misleading results, so BMI is best used alongside measures like waist size and other health checks.
Indian and Asian-Pacific guidelines often use lower cut-offs because South Asians face higher health risks at a lower BMI. A BMI of 18.5 to 22.9 is considered healthy, 23 to 24.9 is overweight (at-risk), and 25 or above is treated as obese. Waist circumference is also closely watched in this population.
Since BMI depends on weight and height, lowering it means gradual, sustainable weight loss: a balanced diet with sensible portions, more whole foods and fibre, fewer sugary and ultra-processed items, regular physical activity, good sleep, and managing stress. Aim for slow, steady progress rather than crash diets, and consult a doctor or dietitian before starting a major weight-loss plan.
No. Children and teenagers should be assessed using age- and sex-specific BMI growth charts rather than adult categories. BMI is also not used for pregnant women, since healthy pregnancy weight gain would skew the result. Older adults can also get less reliable readings. These groups should rely on guidance from a healthcare professional.
BMI is a screening signal, not a diagnosis. If your BMI falls outside the healthy range, if it concerns you, or if you are planning significant changes to your weight, diet, or exercise, it is wise to consult a doctor or qualified dietitian. They can evaluate your full health picture and give advice tailored to you.