AHI Calculator (Apnea-Hypopnea Index)
Calculate your Apnea-Hypopnea Index (AHI) and see your sleep apnea severity category.
😴 What is the AHI Calculator?
The AHI calculator computes the Apnea-Hypopnea Index, the number of apnea and hypopnea breathing events per hour of sleep, and classifies the result into standard clinical severity categories used to diagnose obstructive sleep apnea.
Sleep medicine physicians and sleep study technicians use AHI as the primary metric from an overnight polysomnography or home sleep apnea test. This calculator lets you apply the same formula to event counts and sleep time you already have, such as from a sleep study report, to see the resulting AHI and severity category.
A common misconception is that this calculator can diagnose sleep apnea on its own. It cannot, AHI must be measured during an actual sleep study using specialized breathing and oxygen sensors, and a full diagnosis considers AHI alongside symptoms, oxygen desaturation levels, and other clinical findings.
This tool is useful for understanding a sleep study result you have already received, translating the raw event counts and sleep duration into the standard AHI number and severity label used in clinical reports.
📐 Formula
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 - 22 apneas, 20 hypopneas, 7 hours sleep
Example 2 - 70 apneas, 50 hypopneas, 6 hours sleep
Example 3 - 10 apneas, 8 hypopneas, 7.5 hours sleep
❓ Frequently Asked Questions
🔗 Related Calculators
What is the Apnea-Hypopnea Index (AHI)?
AHI is the number of apnea and hypopnea events per hour of sleep, recorded during a sleep study. It is the primary metric used to diagnose and classify the severity of obstructive sleep apnea. AHI = (apneas + hypopneas) / total sleep hours.
What AHI score indicates sleep apnea?
An AHI below 5 is considered normal. An AHI of 5 to 14 indicates mild sleep apnea, 15 to 29 indicates moderate sleep apnea, and 30 or more indicates severe sleep apnea, according to standard clinical severity thresholds.
What is the difference between an apnea and a hypopnea?
An apnea is a complete or near-complete pause in breathing lasting at least 10 seconds. A hypopnea is a partial reduction in airflow (typically 30% or more) lasting at least 10 seconds, combined with a drop in blood oxygen or an arousal from sleep. Both count equally toward the AHI.
How is AHI different from RDI (Respiratory Disturbance Index)?
AHI counts only apneas and hypopneas. RDI additionally includes respiratory effort-related arousals (RERAs), breathing disturbances that cause a sleep arousal without meeting the full criteria for an apnea or hypopnea. RDI is always equal to or higher than AHI for the same sleep study.
Can I calculate my own AHI without a sleep study?
No. AHI requires precise measurement of breathing pauses and airflow reduction using specialized sensors during an overnight polysomnography or home sleep apnea test. This calculator applies the formula to event counts a sleep study has already measured, it cannot generate those counts itself.
What happens after a high AHI result?
A sleep medicine physician reviews the full sleep study, not just AHI alone, and discusses treatment options which may include CPAP (continuous positive airway pressure) therapy, oral appliances, lifestyle changes, or in some cases surgery, depending on severity and the specific type of sleep apnea diagnosed.
Does a low AHI mean I do not have sleep apnea?
An AHI below 5 generally indicates no sleep apnea by AHI criteria alone, but a sleep physician also considers symptoms, oxygen desaturation levels, and other findings, since some people have significant symptoms with a borderline AHI, or upper airway resistance syndrome that AHI alone does not fully capture.
Is a higher AHI always more dangerous?
Generally, yes, higher AHI is associated with greater cardiovascular risk and more severe daytime symptoms, but the relationship also depends on the severity and duration of oxygen desaturation during each event, not just the event count alone, which is why sleep specialists review the complete study.
Can AHI change over time?
Yes. AHI can fluctuate with weight changes, alcohol use, sleep position, nasal congestion, and age. Significant weight loss or gain, in particular, commonly changes AHI meaningfully, which is why repeat sleep studies are sometimes recommended after major life or health changes.
Does body position affect AHI?
Yes, significantly for many people. Sleep apnea events are frequently more frequent and severe when sleeping on the back (supine position) due to gravity's effect on the airway, and some sleep studies report a separate supine AHI alongside the overall AHI.