MSMuhammad Shahid

Free tool · runs in your browser

BMI calculator

Calculate your body mass index from your weight and height, and see your category and healthy weight range.

For adults aged 20 and over. BMI is a screening number, not a diagnosis: it does not measure body fat directly. For medical advice, see a doctor. Children and teenagers need age-specific charts.

Quick answer

BMI is your weight in kilograms divided by your height in metres squared. So 70 kg at 1.75 m gives 70 ÷ 3.0625 = 22.9. The WHO adult categories are: under 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight, and 30 or more obesity. BMI is a screening number rather than a diagnosis, so talk to a doctor about your health.

How to use it

  1. Choose your units. Metric (kg and cm) or US (lb, feet and inches).
  2. Enter weight and height. The result appears straight away.
  3. Read your result. See your BMI, its category and the healthy weight range for your height.

Example

An adult weighing 70 kg at a height of 175 cm:

Input

Weight: 70 kg
Height: 175 cm

Output

BMI: 22.9
Category: Healthy weight
Healthy range: 56.7 kg to 76.3 kg

Common errors and how to fix them

My BMI looks far too high or low
Check the units: 175 goes in as centimetres rather than metres, and pounds must not be entered as kilograms.
My BMI says overweight but I am muscular
BMI cannot tell muscle from fat. A waist measurement or body-composition test gives a better picture.

Frequently asked questions

How is BMI calculated?

Metric: weight in kg ÷ (height in m)². US: 703 × weight in lb ÷ (height in inches)². The tool converts US units to metric and gives the same answer.

What is a healthy BMI?

18.5 to 24.9 for most adults, according to the World Health Organization.

Is BMI accurate?

It is a useful population-level screen, but it does not measure body fat directly. Muscular people can score high, and older people with little muscle can score low.

Are the ranges different for Asian adults?

Often, yes. Health risks can begin at a lower BMI in many Asian populations, and a WHO expert group suggested extra action points at 23 and 27.5. Some countries use lower cut-offs.

Can children use this calculator?

No. Under-20s need age- and sex-specific growth charts. Ask a paediatrician or use your health service's child calculator.

Does BMI apply during pregnancy?

No. Weight changes in pregnancy make it unreliable. Doctors usually use your pre-pregnancy BMI.

What else should I check besides BMI?

Waist measurement, blood pressure, blood sugar and cholesterol tell you more about health risk. A doctor can interpret them together.

Is my data saved?

No. Your weight and height stay in your browser and are not stored or sent.

How do I convert pounds and feet for BMI?

Choose US units and enter them directly. The tool converts them to kilograms and metres for you: 1 lb is 0.4536 kg and 1 inch is 2.54 cm.

Does BMI change with age?

The adult formula is the same from age 20, although body composition changes with age. To check an exact age, use the age calculator.

Sources

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By Muhammad Shahid. Last updated .