About BMI Tracker
BMI Tracker is a free BMI index calculator that works instantly in your browser. Our goal is simple: help you find your Body Mass Index, read it against a clear BMI index chart, and understand what the number does - and does not - mean, with no signups, clutter, or confusing medical jargon.
Why we built BMI Tracker
BMI is one of the most searched-for health numbers, yet many calculators bury the result in ads, ask for personal details, or skip the context that makes the number useful. We built BMI Tracker as a fast, private alternative: enter your height and weight, get a clear result, and read a plain-language explanation grounded in trustworthy sources. Whether you want a quick check or a number to track over time, the tool gives you the same accurate BMI math used by health authorities.
What is the BMI index?
The BMI index, or Body Mass Index, is a single number calculated from your height and weight. In metric units it is your weight in kilograms divided by your height in metres squared; in US units it is your weight in pounds divided by your height in inches squared, multiplied by 703. The BMI index is widely used as a screening tool because it is easy to measure and applies to most adults, but it does not measure body fat directly or diagnose any condition.
BMI index chart
The BMI index chart below shows the standard adult categories used for ages 20 and older, published by the U.S. Centers for Disease Control and Prevention (CDC). Find the range your number falls into to see your category at a glance.
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Healthy Weight | 18.5 - 24.9 |
| Overweight | 25.0 - 29.9 |
| Obesity | 30.0 and above |
| Class 1 Obesity | 30.0 - 34.9 |
| Class 2 Obesity | 35.0 - 39.9 |
| Class 3 Obesity | 40.0 and above |
Children and teens aged 2 to 19 are read differently: their BMI is interpreted with age- and sex-specific percentiles rather than these fixed ranges. If you are calculating for a young person, use our child BMI calculator and the BMI calculator by age for the right guidance.
Using the BMI index calculator
Our BMI index calculator runs entirely on your device and supports both measurement systems. Switch between US and metric units, enter your height and weight, and your BMI and category appear instantly alongside a small gauge that points to where your result sits on the scale. Explore the version that matches how you search:
- BMI calculator - the main tool with US and metric units.
- Online BMI calculator - fast, no signup, runs in your browser.
- BMI calculator in kg - metric-first using kilograms and centimetres.
- BMI calculator by age - adults 20+ and children and teens 2 to 19.
New to BMI? Our BMI FAQ answers the most common questions, from what BMI stands for to what counts as a healthy or good BMI index.
How we keep information accurate
Our calculators use the standard BMI formulas and the adult categories published by the U.S. Centers for Disease Control and Prevention (CDC) and the National Heart, Lung, and Blood Institute (NIH/NHLBI). For children and teens, we follow the principle that BMI must be interpreted with age- and sex-specific percentiles, and we direct families to the official CDC tool rather than estimating percentiles ourselves.
What BMI Tracker is not
We are not a medical provider, and our content is not medical advice. The BMI index is a screening tool, not a diagnosis. For any personal health question, please speak with a qualified healthcare professional. You can read more in our Medical Disclaimer.
Your privacy
The calculators run entirely on your device. We never receive, store, or sell the height, weight, or age you enter. See our Privacy Policy for details.
Get in touch
Questions or feedback? Visit our Contact page. We welcome corrections that help us keep the information accurate.