BMI Calculator
BMI calculator for adults: check your body mass index in metric or imperial units, see WHO and Asian (Indian) categories and your healthy weight range.
Written by HealthSensibly Editorial TeamReviewed by the HealthSensibly editorial teamUpdated
BMI Calculator
Calculated on your device — your numbers are never sent to us.
An educational estimate — not a diagnosis, and not personal medical advice.
Understanding your BMI result
Body Mass Index (BMI) is found by dividing your weight in kilograms by the square of your height in metres. Doctors around the world use it as a fast screening figure, but it is not a direct measurement of how much body fat you carry.
| BMI | WHO category for adults |
|---|---|
| Under 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25 – 29.9 | Overweight |
| 30 or higher | Obesity |
Worth keeping in mind
- Several Asian health authorities apply lower thresholds, counting overweight from a BMI of 23.
- A very muscular build can push BMI up even when body fat is not high.
- It is not intended for use in pregnancy or for children and teenagers.
How the BMI calculator works
Body Mass Index compares your weight with your height. The calculator squares your height in metres and divides your weight in kilograms by that number:
- Metric: BMI = weight (kg) ÷ height (m)²
- Imperial: BMI = 703 × weight (lb) ÷ height (in)²
A worked example: someone who is 1.62 m tall and weighs 62 kg has a BMI of 62 ÷ (1.62 × 1.62) = 23.6. That result is in the healthy band on the international scale but in the overweight band on the Asian scale described below — which is why the calculator shows both.
What your BMI number means
The World Health Organization uses the same adult bands for women and men. They describe groups of people, not one person, so read your number as a starting point for a conversation rather than a label.
| BMI (adults) | WHO category | Asian / Indian category |
|---|---|---|
| Below 18.5 | Underweight | Underweight |
| 18.5 – 22.9 | Healthy weight | Healthy weight |
| 23.0 – 24.9 | Healthy weight | Overweight |
| 25.0 – 29.9 | Overweight | Obesity |
| 30.0 – 34.9 | Obesity class I | Obesity |
| 35.0 – 39.9 | Obesity class II | Obesity |
| 40 and above | Obesity class III | Obesity |
Why Indians and other Asians use lower cut-offs
At the same BMI, people of South Asian origin tend to carry more body fat, and more of it around the abdomen, than people of European origin. Type 2 diabetes, high blood pressure and heart disease therefore start to rise at lower numbers. A WHO expert consultation in 2004 flagged 23 and 27.5 as action points for Asian populations, and the 2009 Indian consensus guidelines count 23–24.9 as overweight and 25 or more as obesity. Our Asian BMI calculator shows these bands side by side.
Waist size adds what BMI misses. For South Asian adults, a waist above about 80 cm (31.5 in) for women or 90 cm (35.5 in) for men is linked with higher metabolic risk — check yours with the waist-to-hip ratio calculator.
Women, men, older adults, athletes and pregnancy
- Women and men share the same adult bands, but at an identical BMI women usually have a higher share of body fat. Two people with the same number can have very different health pictures.
- Adults over 65: some studies find the lowest risk at a slightly higher BMI than in younger adults, and unplanned weight loss matters more than a single reading. Doctors also look at grip strength, walking speed and appetite.
- Athletes and people who lift weights can score as overweight because muscle is dense. A tape measure or a body fat estimate gives a fairer picture.
- Pregnancy: BMI is not used to judge weight while pregnant. Your pre-pregnancy BMI sets the healthy gain range instead — see the pregnancy weight gain calculator.
- Children and teenagers are compared with others of the same age and sex using percentiles; use the child BMI calculator for anyone under 20.
What BMI cannot tell you
BMI does not separate fat from muscle or bone, does not show where fat sits, and says nothing about blood pressure, blood sugar, cholesterol, fitness, sleep or mental health. A person with a “healthy” BMI can still have high visceral fat, and a person with a high BMI can be fit and metabolically healthy. That is why we pair the number with a healthy weight range for your height, which is easier to plan around than a single figure.
When to talk to a doctor
- your BMI is under 18.5, or you are losing weight without trying
- your BMI is 25 or more (23 or more on the Asian scale) and you also have a large waist, high blood pressure, raised blood sugar or a family history of diabetes or heart disease
- your BMI is 35 or above, or weight is affecting your joints, breathing or sleep
- food, eating or body image are causing you distress
A doctor can check the numbers BMI cannot, such as HbA1c, lipids and blood pressure, and suggest a plan that suits you. If you want a gentle place to start, try the weight loss calculator or a free 7-day diet plan.
Common questions
What is a healthy BMI for Indians?
For Indian and other South Asian adults a BMI of 18.5 to 22.9 is considered healthy. Indian guidelines treat 23 to 24.9 as overweight and 25 or above as obesity, which is lower than the international cut-offs of 25 and 30.
Is BMI different for men and women?
No, adult women and men use the same BMI bands. Women usually carry more body fat than men at the same BMI, so waist size and other checks help to complete the picture.
Is BMI accurate for people with a lot of muscle?
Not very. Muscle weighs more than fat for its size, so athletes and people who lift weights can be classed as overweight while carrying little fat. A waist measurement or body fat estimate is more useful for them.
Can I use this BMI calculator during pregnancy?
It is not meant for pregnancy. Doctors use your BMI from before pregnancy to set a healthy range of weight gain instead; our pregnancy weight gain calculator does this for you.
Can children use the adult BMI calculator?
No. Children and teenagers are still growing, so their BMI is compared with others of the same age and sex as a percentile. Use the child BMI calculator for anyone aged 2 to 19.
How often should I check my BMI?
Every few months is plenty for most adults. Weight can swing by a kilo or more from day to day with water and food, so a long-term trend tells you more than a single weighing.
Sources: WHO: Obesity and overweight fact sheet · WHO expert consultation: BMI for Asian populations (Lancet 2004) · Misra A et al. Indian consensus statement on obesity (JAPI 2009) · NIH NHLBI: Assessing your weight and health risk · CDC: About adult BMI
Checked against the sources listed. This is general health information, not a diagnosis or personal medical advice — please speak to your doctor about your own situation.
Who wrote and checked this
Our editors write every tool explainer and guide in plain language from current guidelines and research, and list the sources on the page.
We check every tool and guide against the sources listed on the page and update it when guidance changes.
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