Free CPAP tool
AHI Calculator
AHI is the number of apneas and hypopneas per hour. Enter the counts and the hours they were counted over. For a sleep study use total sleep time; for a CPAP report use the hours the machine was running.
Formula
AHI = (apneas + hypopneas) / hours. A sleep lab divides by total sleep time; a CPAP machine divides by the time the machine was running, so its figure is an estimate. Adult bands: under 5 normal, 5 to under 15 mild, 15 to under 30 moderate, 30 or more severe.
Worked example
42 apneas + 30 hypopneas = 72 events over 7.2 hours. AHI = 72 / 7.2 = 10 events per hour, which falls in the mild band (5 to under 15).
Assumptions and limits
- Machine-reported AHI uses usage hours and the machine's own event detection, which is not the same as a scored sleep study.
- Hypopnea scoring rules differ between labs, which changes AHI.
- Children use different thresholds; this calculator is for adults.
Only a sleep test can tell. Home sleep tests are a common first step for adults without other major health conditions; your doctor can order one, or you can use an online service that includes a clinician review.
Supplies that can help
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A soft strap that supports the jaw to help keep the mouth closed, used mainly with nasal and nasal pillow masks to reduce mouth leaks.
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Frequently asked questions
What is a good AHI on CPAP?
Under 5 events per hour is the normal range for adults. If your machine keeps showing an AHI above 5, or it rises suddenly, tell your prescribing clinician; do not change your pressure yourself.
Why is my CPAP AHI different from my sleep study?
The sleep study divides by measured sleep time and is scored by a technologist; the machine divides by run time and detects events from airflow. Leaks can also make a machine miss or miscount events.
Does AHI include central apneas?
Yes, AHI counts all apneas plus hypopneas. Many machines split them out. A rising count of central or clear-airway events is something to raise with your clinician.
Sources
Last reviewed October 11, 2026. How we research · Report an error