Asthma Zone Calculator


This calculator is for people with asthma. To use this tool, you must know your peak flow number. Your peak flow is how fast you exhale air after taking a deep breath. Your peak flow tells you and your doctor how well your lungs are working.

You need to know your personal best peak flow number to help control your asthma. Changes from your personal best can help you see how well your asthma is under control. These changes also can let you know when you need medication and when you need medical care. This calculator will determine your Green, Yellow and Red Zones, based on your personal best peak flow number.

If you don't know your personal best peak flow number, or don't know how to find it, click here for an explanation.

Enter Your Information

What is your personal best peak flow number?


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This calculator is not intended to replace the evaluation of a health care professional.

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The information provided in this Web site is for informational purposes only. It is not a substitute for medical advice. All medical information presented should be discussed with your healthcare professional. See additional Terms of Use at For more information, call 1.866.CALL.MLH.