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How to measure your peak flow

Peak flow meters come in many shapes and sizes, but they work about the same. Follow these steps to measure your peak flow.

Three different peak flow meters set to their lowest number.

1. Set the pointer of the peak flow meter to 0 or the lowest number on the meter.

A mouthpiece and a peak flow meter.

2. If there is a separate mouthpiece, attach it to the meter.

A person taking a deep breath to get ready to use the peak flow meter.

3. Sit up or stand up as straight as you can. Take a deep breath.

A person with a peak flow meter mouthpiece in their mouth.

4. Close your lips tightly around the mouthpiece. Keep your tongue away from the mouthpiece. Keep your fingers away from the number scale.

A person breathing out hard into the peak flow meter.

5. Blow out as hard and as fast as you can.

Three peak flow meters with different results.

6. Note the number on the meter, and write it down. Do the test 2 more times. The highest of these 3 tests is your peak flow.

Current as of: May 1, 2026

Author: WebMD Ignite Staff
Clinical Review Board
All WebMD Ignite education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

Current as of: May 1, 2026

Author: WebMD Ignite Staff

Clinical Review Board
All WebMD Ignite education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

This information does not replace the advice of a doctor. WebMD Ignite, disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Learn how we develop our content.