Children's Asthma Peak Flow Calculator
Some people use peak flow meters to monitor changes in asthma. Peak flow readings show how well a child's lungs are working. This calculator shows the predicted peak flow in children. With your child's height, you can find his or her predicted peak flow. Predicted peak flow is how much air a child of a certain height is expected to breathe out (exhale) after taking a deep breath.
An even more important number is your child's personal best peak flow. This number helps monitor your child's asthma. Changes from your child's personal best help you see how well your child's asthma is controlled. These changes also can let you know when your child needs medicine and when your child needs medical care.
If you don't know how to find it, click here for an
Note: The minimum height for this calculator is 44 inches.
Finding Your Child's Personal Best Peak Flow
Your child's personal best peak flow is the highest peak flow number your child can measure over 2 to 3 weeks. Write down your child's personal best during this time, when his or her asthma is controlled.
Here's how to find out your child's personal best peak flow:
- Take peak flow readings at least two times a day for 2 to 3 weeks.
- Take the readings between noon and 2 p.m. each day.
- If your child uses quick-relief medication, take the readings after your child uses this
- If your child's health care provider want you to check peak flow at other times, make sure you do.
- Write down all of the readings.
- The highest peak flow over the 2 to 3 weeks is your child's personal best.
Once you know your child's personal best peak flow, you and your child can work with his or her health care provider to figure out the peak flow ranges for each of the asthma action plan zones.
If you don't have an asthma action plan for your child or if his or her plan is not up to date, make sure you talk with your child's provider.
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Your Child's Results
Because your child's height is , his or her predicted peak flow is .
What are asthma action zones?
Asthma action plans are divided into zones. Each zone gives symptoms and peak flow ranges and what actions to take.
- The Green Zone.
A peak flow of 80% to 100% of your child's personal best. It means your child's asthma is in good control. It
means your child currently has no symptoms. Your child should continue to take his or her medication as
- The Yellow Zone. A peak flow of 50% to 79% of your child's personal best. This means caution. Your child's asthma is not in good control.
Your child should take his or her quick-relief medicine.
- The Red Zone. A
peak flow of less than 50% of your child's personal best. This is an emergency. Your child should
take his or her quick-relief medicine right away. Call your child's health care provider or 911, or go to the closest emergency department.
This calculator is not intended to replace the evaluation of a health care professional.
Online Medical Reviewer:
Holloway, Beth, RN, MEd
Online Medical Reviewer:
MMI board-certified, academically affiliated clinician
Date Last Reviewed: