BMI Calculator works out your Body Mass Index, which is your weight in kilograms divided by the square of your height in metres. Doctors and health organisations use BMI as a quick screening tool to see whether a person's weight is in a healthy range for their height.
Enter your weight and height in metric or imperial units, and the calculator shows your BMI, your weight category based on World Health Organization (WHO) cut-offs, and the weight range considered healthy for your height.
How to use the BMI Calculator tool
- Choose metric or imperial units.
- Enter your weight and height.
- Read your BMI and category, which update as you type.
- Check the healthy weight range for your height.
Features
- Metric (kg/cm) and imperial (lb/ft/in) units.
- WHO adult categories, from underweight to obesity class III.
- Healthy weight range for your height.
- Instant results with no submit button.
- Private: nothing is stored or sent.
Tips for best results
BMI doesn't distinguish between muscle and fat, so very muscular people may get a high BMI while being healthy, and older adults may have a 'normal' BMI with low muscle mass. Some health bodies suggest lower cut-offs for people of South Asian and East Asian descent (for example, 23 for overweight). Waist measurement adds useful information. Talk to a healthcare professional for personal advice.
BMI was devised in the 19th century by the Belgian mathematician Adolphe Quetelet and is still widely used because it is quick and needs no equipment. It is best seen as a starting point for a conversation about health, used alongside measurements such as waist circumference, blood pressure and activity levels.
Compatibility and limits
The BMI Calculator gives results instantly as you type and works on phones, tablets and computers. Results are rounded for display but calculated at full precision. The numbers you enter are not saved, so refreshing the page starts a new calculation. Results are estimates for general information, so for important medical, legal or financial decisions, please check with a qualified professional.
Privacy: your files never leave your device
All calculations happen in your browser. The numbers you enter, such as dates of birth, weights or loan amounts, are never sent to a server or stored.
Frequently asked questions
What is a healthy BMI?
For most adults, a BMI from 18.5 to 24.9 is considered a healthy weight range by the WHO.
How is BMI calculated?
BMI = weight (kg) ÷ height (m)². In imperial units: 703 × weight (lb) ÷ height (in)².
Is BMI accurate for everyone?
No. It's a screening tool and doesn't account for muscle mass, age, sex or ethnicity.
Can children use this calculator?
No. Children and teens need age- and sex-specific BMI percentiles.
Is my data private?
Yes. The calculation runs entirely in your browser.