AHI Calculator
Calculate your Apnea-Hypopnea Index and sleep apnea severity using AASM guidelines
Complete breathing cessations lasting 10+ seconds recorded during the sleep study
Partial airflow reductions of 30%+ for 10+ seconds, with O2 desaturation or arousal
Actual verified sleep time from EEG, not time in bed or recording time
Compare pre- and post-treatment AHI
Enter Your Sleep Study Data
Input your apnea and hypopnea events along with total sleep time to calculate your Apnea-Hypopnea Index.
How to Use This AHI Calculator
Select Patient Type and Enter Event Counts
Choose whether you are calculating for an adult or a child under 13. Then enter the total number of apnea events and hypopnea events recorded during your sleep study. These numbers come from your polysomnography (PSG) report or home sleep test results. Apnea events are complete breathing cessations lasting 10+ seconds; hypopnea events are partial reductions in airflow of 30% or more lasting 10+ seconds with associated oxygen desaturation or arousal.
Enter Total Sleep Time
Input your total sleep time using either hours or minutes — toggle the unit to match your report. Use actual verified sleep time from your sleep study report, not time in bed or recording time. For polysomnography, sleep time is determined by EEG monitoring. Entering recording time instead of sleep time will underestimate your true AHI. Typical adult sleep study recordings last 7-8 hours, but actual sleep time may be 5-7 hours.
Review Your AHI Score and Severity Classification
Your AHI is calculated instantly and displayed with its severity category based on AASM guidelines. Review the severity gauge to see where your score falls on the Normal-Mild-Moderate-Severe scale. Check the calculation breakdown for apnea events per hour, hypopnea events per hour, and total event breakdown. Read the clinical interpretation and treatment recommendation for your severity level, and review the oxygen saturation reference associated with your classification.
Use CPAP Tracker to Monitor Treatment Progress
If you are on CPAP therapy, enable the CPAP Effectiveness Tracker by toggling the option below the main inputs. Enter your pre-treatment AHI from your diagnostic sleep study and your current CPAP-treated AHI from your titration study or CPAP device reporting. The calculator will show your improvement percentage and whether you have met the treatment target of AHI under 5 events per hour. Use Export CSV to save your results for tracking over time or sharing with your doctor.
Frequently Asked Questions
What is a good AHI score?
For adults, an AHI below 5 events per hour is considered normal with no clinically significant sleep-disordered breathing. An AHI of 5 to 14.9 indicates mild sleep apnea, 15 to 29.9 indicates moderate sleep apnea, and 30 or above indicates severe sleep apnea. For people on CPAP therapy, the treatment target is typically an AHI below 5, regardless of the original pre-treatment severity. Some specialists aim for an even lower treated AHI of under 2 events per hour for optimal symptom control. For children, thresholds are much stricter — a normal AHI is under 1 event per hour, and even mild elevations should prompt evaluation by a pediatric sleep specialist, because children are more sensitive to the developmental impacts of sleep-disordered breathing.
How does AHI differ from RDI?
AHI (Apnea-Hypopnea Index) counts only apnea and hypopnea events per hour. RDI (Respiratory Disturbance Index) is a broader metric that adds Respiratory Effort-Related Arousals (RERAs) — events where increased breathing effort causes a brief arousal from sleep without meeting the full criteria for an apnea or hypopnea. Because RDI includes more event types, it is always equal to or greater than AHI. A patient can have a normal AHI but an elevated RDI, indicating Upper Airway Resistance Syndrome (UARS), which causes daytime sleepiness and fragmented sleep despite a low AHI. If you have significant symptoms but a borderline or normal AHI, ask your sleep specialist whether your RDI was also measured and reported.
Why might my home sleep test AHI be lower than my lab AHI?
Home sleep tests (also called Level III portable monitoring devices) use total recording time as the denominator for AHI calculation, because they cannot verify actual sleep time without EEG monitoring. In-laboratory polysomnography uses EEG-verified actual sleep time, which is always shorter than recording time since you are not sleeping every minute you are in bed. Because dividing by a larger number produces a smaller result, home test AHI values are typically 10 to 15% lower than the AHI that would be measured for the same patient in a laboratory. If your home test result is near a threshold — for example, 4.5 or 14 events per hour — your true severity category may actually be one level higher. Sleep specialists are trained to account for this difference when interpreting home sleep test results.
Does AHI vary from night to night?
Yes, significantly. AHI can vary from night to night in the same individual due to several factors. Body position during sleep greatly affects OSA severity — sleeping on your back typically worsens AHI compared to sleeping on your side. Alcohol consumption within 4 hours of bedtime increases muscle relaxation in the throat, raising AHI. Nasal congestion from allergies, colds, or inflammation can worsen both apneas and hypopneas. Sleep stage distribution matters too: REM sleep is associated with lower muscle tone and typically produces more apneas than non-REM sleep. Fatigue, stress, and even the unfamiliar environment of a sleep lab can alter sleep patterns. For these reasons, some specialists recommend multiple nights of monitoring to get a representative AHI, especially when the first-night result falls near a severity threshold. Some CPAP devices track nightly AHI, allowing patients to monitor variability over time.
What CPAP AHI should I aim for?
The standard clinical treatment target for CPAP therapy is an AHI below 5 events per hour, which corresponds to the normal range on the adult severity scale. Most guidelines define effective CPAP therapy as achieving an AHI below 5. However, many sleep specialists and patients aim for even lower values — below 2 events per hour — for maximum symptom relief, particularly for individuals with severe daytime sleepiness or significant cardiovascular risk factors. Research has demonstrated that effective CPAP therapy reduces AHI by approximately 73% on average. If your treated AHI remains above 5 despite consistent CPAP use, you should contact your sleep medicine provider to evaluate mask fit, pressure settings, device type (CPAP vs. auto-titrating APAP vs. BiPAP), and underlying factors such as positional apnea or central events that may require a different treatment approach.
What are the health risks of untreated sleep apnea?
Untreated obstructive sleep apnea carries substantial long-term health risks beyond daytime fatigue and poor sleep quality. The repetitive cycles of oxygen desaturation and sleep arousal create chronic cardiovascular stress. Studies have linked untreated OSA with a significantly elevated risk of hypertension — up to 37% of OSA patients have difficult-to-control high blood pressure. Approximately 70% of patients who experience a heart attack and 65% of stroke patients have concurrent sleep apnea with AHI above 10. Type 2 diabetes risk is increased by insulin resistance caused by chronic sleep deprivation and intermittent hypoxia. Cognitive impairment, including memory problems and reduced executive function, is strongly associated with moderate to severe untreated OSA. Additionally, untreated sleep apnea dramatically increases the risk of motor vehicle accidents due to excessive daytime sleepiness — some studies estimate the risk is 2.5 to 7 times higher than in the general population.