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
Instructions for Determining Your Personal Best Peak Flow Number
Your personal best peak flow number is the highest peak flow number you can measure every day
to three weeks. You should take these measurements only when your asthma is in good control.
Good control means you don't currently have any symptoms of asthma.
Each person's asthma is different, and each person's personal best peak flow number is different.
Even among people of the same height, weight and sex, peak flow numbers can differ.
Here's how to determine your personal best peak flow number:
- Take peak flow readings at least two times a day for two to three weeks.
- Take the readings when you wake up and again between noon and 2 p.m.
- If you use quick-relief medication, take the readings before and after you use this medicine.
Talk to your doctor before measuring your personal best peak flow number. He or she may have
other instructions or suggestions, based on your condition.
Once you know your personal best peak flow number, you can use this calculator or ask your doctor
to help determine the values for your Green, Yellow and Red Zones.
Close this section
Your ResultsHere are the peak flow values for your different asthma zones.
Your Green Zone is above percent. (80 to 100 percent of your personal best)
What the Green Zone means:
The Green Zone is a sign that your asthma is in good control. It means you currently have no symptoms of asthma. You should continue to take your medication as usual.
Your Yellow Zone is below percent. (50 to 79 percent of your personal best) liters/minute.
What the Yellow Zone means:
The Yellow Zone is your caution signal. It means you need to take your quick-relief medicine from the instructions on your written asthma plan of action. The Yellow Zone also means your asthma may not be in good control. Ask your doctor if you need to change or increase your daily medications.
Your Red Zone is anything below percent. (Less than 50 percent of your personal best)
What the Red Zone means:
The Red Zone is your emergency signal. Take or increase your quick-relief medicine immediately, according to the instructions on your written plan of action. Then, call your doctor to find out what to do.