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BMI Calculator – Free Body Mass Index Tool
Use this free BMI calculator to check your body mass index in seconds. Enter your height and weight, choose metric or imperial units, and see your BMI and category right away. It runs in your browser, so your numbers stay private.
What Is BMI?
BMI stands for Body Mass Index. It is a simple number that compares your weight to your height. Doctors and health websites use it as a quick way to check if your weight may be too low, healthy, or too high for your height.
BMI is a screening tool. It does not measure body fat directly, and it cannot tell you everything about your health.
How to Use the BMI Calculator
- Choose your units: metric (kg and cm) or imperial (lb and ft/in).
- Enter your height.
- Enter your weight.
- See your BMI number and your BMI category.
It takes less than a minute. No sign-up and no installation needed.
BMI Formula
Metric: BMI = weight (kg) ÷ height (m) ÷ height (m)
Imperial: BMI = 703 × weight (lb) ÷ height (in) ÷ height (in)
Example: A person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9. This is in the healthy range.
BMI Categories (Adults)
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Normal (healthy) weight |
| 25.0 to 29.9 | Overweight |
| 30.0 and above | Obese |
These ranges are used by the World Health Organization (WHO) for adults.
Why Use Our BMI Calculator?
- Free forever: No limits and no hidden charges.
- Metric and imperial: Use kg/cm or lb/ft, whichever you prefer.
- Clear result: You get your BMI number and category together.
- 100% private: Everything runs in your browser. Nothing is uploaded or saved.
- Works on all devices: Mobile, tablet, and desktop.
Limits of BMI
BMI is helpful, but it is not perfect. Keep these points in mind:
- It does not separate muscle from fat. Athletes and gym lovers may show a high BMI even when they are healthy.
- It does not show where fat is stored in your body.
- It is not made for children and teenagers. Kids need BMI-for-age charts from a doctor.
- It may not be accurate during pregnancy or for older adults.
If you want to track how your weight changes over time, our Percentage Calculator can help you find the percentage gain or loss easily. For more simple guides, visit our blog, or explore all free tools on MeraTool.
Frequently Asked Questions (FAQ)
What is a BMI calculator?
A BMI calculator uses your height and weight to work out your body mass index and show which weight category you fall in.
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered a healthy range.
How do I calculate BMI?
Divide your weight in kilograms by your height in meters squared. Or just enter your numbers in the calculator above and it does the math for you.
Is this BMI calculator free?
Yes. It is completely free, and you do not need an account.
Is my data safe?
Yes. The calculator runs entirely in your browser. Nothing you enter is uploaded or stored on our servers.
Can I use pounds and feet instead of kg and cm?
Yes. You can switch between metric and imperial units.
Is BMI accurate for athletes?
Not always. Muscle weighs more than fat, so athletes can have a high BMI without having too much body fat.
Can children use this BMI calculator?
This calculator is made for adults. Children and teens should be checked with BMI-for-age charts by a doctor.
Do the BMI ranges change for different people?
Some health groups use lower cut-off numbers for people of South Asian background, because health risks can start at a lower BMI. Ask your doctor which range is best for you.
Does BMI tell me if I am healthy?
Not completely. BMI is only a quick check. Diet, exercise, sleep, blood tests, and family history also matter.
Important Note
This BMI calculator is for general information only. It is not medical advice. Please talk to a doctor or qualified health professional before making any health decisions.