For adults age 20 and older
Adult BMI Calculator
Calculate your adult BMI, understand the screening category, and track changes over time.
Your measurements
Enter your height and weight. Your result updates instantly.
Your result
Healthy weight
Healthy adult range: 18.5–24.9
BMI is a screening measure, not a diagnosis. Consider it together with other health information.
Trends
0 of 1,000 measurements
Review up to 1,000 saved measurements. Each BMI is recalculated from its height and weight.
No measurements yet
Save the current result or add a dated measurement to start your trend.
What BMI can—and cannot—tell you
Body mass index (BMI) relates weight to height and places the result in a broad adult screening category. It is a quick way to add context to a measurement and to watch its direction over time. BMI does not directly measure body fat, fitness, or overall health, and it cannot diagnose a medical condition.
Adult BMI screening categories
The ranges below are intended for adults age 20 and older. Their colors match the range dial and saved-history table.
| BMI | Classification |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to below 25 | Healthy weight |
| 25 to below 30 | Overweight |
| 30 to below 35 | Obesity, class 1 |
| 35 to below 40 | Obesity, class 2 |
| 40 or above | Obesity, class 3 |
The category is only one piece of context. Muscle mass, pregnancy, age-related changes, medical history, health behaviors, physical findings, and laboratory results can all affect how a result should be understood. Discuss personal questions with a qualified healthcare professional. The CDC adult BMI guidance explains the categories and their limits in more detail.
How BMI is calculated
For metric measurements, BMI is weight in kilograms divided by height in metres squared:
For US customary measurements, the same relationship uses a conversion factor:
Switching unit systems does not change the underlying measurement; the calculator converts the values for you.
Use the calculator, history, and exports
- Choose Metric or US units and enter height and weight.
- Read the result and range as soon as both measurements are valid—there is no calculate button.
- Select Save measurement to add the current result and time to the history on this device.
- Use the table to add, edit, or delete dated measurements, or switch to the chart to see the trend.
- Use Export to download the visible history columns as CSV or Excel. The active unit system is used in the exported file.
- If desired, select the cloud control and sign in to sync the history with your ZestCalc account. Cloud sync is optional and stores measurements as readable account data.
A trend can provide more context than a single reading. Take measurements under similar conditions when possible, and focus on the longer-term direction rather than small day-to-day changes.
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