BMI Calculator

What is BMI? What is BMI index and BMI calculator meaning

BMI, or body mass index, is a simple number that compares your weight with your height. It is calculated as weight in kilograms divided by height in metres squared. Doctors, insurers and fitness trainers use it as a quick screening test for underweight, overweight and obesity in adults. This free BMI calculator works out your BMI in one step, shows the WHO weight category and the Asian-Indian category used in India, and tells you the healthy weight range for your exact height.

It is an online BMI calculator for men and women that accepts kg and cm, kg and feet (the way most people in India know their height) or pounds and feet/inches as used in the US and UK.

How to use this BMI calculator using height and weight

1. Choose your units: kg and cm, kg and feet/inches, or lb and feet/inches.
2. Enter your weight, ideally in the morning before breakfast with light clothing.
3. Enter your height without shoes.
4. Enter your age. For anyone under 20 the result explains how to use BMI-for-age percentiles instead of adult categories.

You instantly see your BMI, your category on both scales, the weight range that gives a normal BMI, and how many kilos you would need to lose or gain to reach it.

BMI formula

How to calculate BMI in cm and kg

BMI = weight (kg) ÷ [height (m)]²

Height in centimetres must first be divided by 100 to get metres.

BMI formula in pounds and inches

BMI = 703 × weight (lb) ÷ [height (in)]²

• weight = body weight in kilograms (or pounds for the imperial formula)
• height = standing height in metres (or inches)
• 703 = conversion factor between the imperial and metric formulas

BMI calculator example: how to calculate BMI of a person

A man weighs 70 kg and is 175 cm tall. His height is 1.75 m, and 1.75² = 3.0625. BMI = 70 ÷ 3.0625 = 22.9, which is in the normal range on the WHO scale. On the Asian-Indian scale 22.9 is still normal, but just below the overweight cut-off of 23. His healthy weight range is 18.5 × 3.0625 = 56.7 kg to 24.9 × 3.0625 = 76.3 kg.

In feet: 5 ft 9 in is 69 inches, or 1.753 m. At 154 lb, BMI = 703 × 154 ÷ 69² = 22.7.

BMI calculator chart: what is BMI range?

BMI calculator for India: why the cut-offs are lower

People of South Asian origin tend to carry more body fat and more fat around the waist at the same BMI as Europeans, and they develop type 2 diabetes and heart disease at lower BMIs. For this reason the WHO expert consultation on Asian populations (2004) and Indian consensus guidelines (2009) recommend that Indian adults treat a BMI of 23 or more as overweight and 25 or more as obese. This BMI calculator for India shows both scales, so whether you are an Indian male or female you can see where you stand on the scale your doctor is likely to use.

BMI calculator for men and women

The adult BMI formula and categories are the same for men and women, so there is no separate male or female BMI calculator. What differs is body composition: at the same BMI, women usually carry more body fat than men. That is why BMI calculator by gender tools show the same number but advise pairing it with waist size. A useful extra check: a waist over 90 cm for Indian men or 80 cm for Indian women (102 cm and 88 cm on Western guidelines) points to higher health risk even with a normal BMI.

Best BMI for men and women

For most adults a BMI between about 18.5 and 24.9 (18.5 to 22.9 for South Asians) is linked with the lowest risk of weight-related disease. There is no single "best" number inside that range.

BMI calculator with age: does age change BMI?

For adults aged 20 and over, the BMI categories do not change with age, so a BMI calculator kg with age uses the same table for a 25-year-old and a 60-year-old. Some research suggests that a slightly higher BMI (up to about 27) is not harmful in people over 65, but guidance still uses the standard ranges. Age matters a great deal for children.

BMI calculator for kids and teens: how to calculate BMI for kids

For children and teenagers (ages 2 to 19), BMI is worked out with the same formula, but it is then compared with other children of the same age and sex on a growth chart. This is called BMI-for-age and is expressed as a percentile:

• Below the 5th percentile – underweight
• 5th to below the 85th percentile – healthy weight
• 85th to below the 95th percentile – overweight
• 95th percentile and above – obesity

In India, paediatricians use the Indian Academy of Pediatrics (IAP) growth charts for children aged 5 to 18 and the WHO charts for younger children. Ask your child's doctor to plot the result rather than using adult categories.

BMI calculator vs body fat percentage

BMI cannot tell muscle from fat. A fit athlete can have a BMI of 27 and little body fat, while an older person with little muscle can have a normal BMI and high body fat. If your BMI and appearance do not match, check your body fat with the body fat calculator, and see a realistic target with the ideal weight calculator. BMI is not valid during pregnancy; use your pre-pregnancy BMI to plan weight gain with your doctor.

Using BMI to lose weight

If your BMI is above the healthy range, a loss of 5–10% of body weight already improves blood pressure, blood sugar and cholesterol. To plan it, find out how many calories you burn with the TDEE calculator and set a daily target with the calorie calculator. A steady loss of about 0.5 kg a week is safe for most adults.

This BMI calculator is for general information and is not medical advice. Speak to a doctor for a full health assessment.

BMI calculator in kg and cm, kg and feet, or pounds

This BMI calculator online free version handles every unit. Kg and cm is the standard used in India and Europe. You can also enter weight in kg with height in feet and inches, the way most Indians know their height, or choose pounds for the US style. The metric formula (kg and cm) and the imperial formula give the same BMI value, so the unit choice only affects convenience.

How to calculate BMI for women and how to calculate BMI for men

The BMI calculator for women uses the same formula and ranges as the one for men. Men and women differ in body fat, not in the maths: a man and a woman with the same weight in kg and the same height get exactly the same BMI. For an Indian man or woman, look at the Asian-Indian row in the result.

BMI calculator by age and gender

For adults, the categories are the same at 25, 45 or 65, so age does not change the result. Children and teens are different: a BMI calculator for kids must use BMI-for-age percentiles by sex, which is why age matters for them but not for adults.

BMI calculator and calories

BMI tells you where your weight stands, not how much to eat. To turn your BMI into a calorie intake, use the calorie calculator for a daily target and a simple diet plan. A BMI calculator to lose weight is most useful when paired with a calorie target.

BMI calculator in Hindi (BMI calculator Hindi)

BMI (body mass index) aapke vajan aur lambai ka anupaat hai. Formula: vajan (kg) ÷ lambai (metre)². Bharat mein 18.5 se 22.9 saamanya, 23 se 24.9 adhik vajan aur 25 ya usse zyada motapa maana jaata hai.

BMI calculator definition and rules

By definition, a BMI calculator divides your weight in kilograms by the square of your height in metres and places the value on a scale of weight categories. The rules behind the result:

• The adult ranges apply from about age 20 (WHO: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obese).
• For Asian Indians, the lower cut-offs of 23 (overweight) and 25 (obese) are used.
• Children and teens are judged by BMI-for-age percentiles, not the adult range.
• BMI is not used during pregnancy, and it can mislead for very muscular people.

BMI calculator calculation, step by step

Weight 70 kg, height 175 cm. Convert height to metres: 1.75. Square it: 1.75 × 1.75 = 3.0625. Divide: 70 ÷ 3.0625 = 22.9. That value is in the normal range on the WHO scale and just below the Asian overweight cut-off of 23.

BMI calculator for women by age

For adult women, the BMI calculator uses the same range at 25, 45 or 70: age does not change the cut-offs. What changes with age is body composition; women tend to lose muscle and gain fat after menopause, so the same BMI can mean more body fat at 60 than at 30. For girls under 18, the BMI calculator for women by age switches to BMI-for-age percentiles.

BMI calculator in kg with age for India

Enter your weight in kg and height in cm or feet. For Indian adults of any age, a BMI of 18.5–22.9 is normal, 23–24.9 overweight and 25 or more obese under the Indian consensus guidelines. For children, Indian doctors use IAP growth charts, as explained above.

BMI calculator for a child: months and teen years

A child's BMI is calculated with the same formula, but the value is compared with other children of the same age in months and sex. Between the 5th and 85th percentile is a healthy weight; the 85th to 95th percentile is overweight and above the 95th is obesity. For example, a BMI of 19 is healthy for a 12-year-old boy but would be in the obese range for a 5-year-old. Ask a paediatrician to plot your child's value on a growth chart.

BMI calculator with body shape: waist size matters too

BMI ignores body shape. Two people with the same BMI can have very different health risks if one carries fat around the waist. Measure your waist at the navel and divide by your height: a waist-to-height ratio under 0.5 is a common healthy target. For Indian adults, a waist above 90 cm in men or 80 cm in women signals abdominal obesity.

BMI calculator app and download

There is no BMI calculator app to download or install: this page works in any phone or desktop browser. Bookmark it or add it to your home screen for one-tap access.

BMI calculator in JavaScript

Developers can write a BMI calculator in JavaScript in one line: const bmi = kg / Math.pow(cm / 100, 2);. For pounds and inches, use 703 * lb / (inches * inches). Round to one decimal with bmi.toFixed(1).

Frequently asked questions

Last updated 2026-09-18