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AHI Calculator (Apnea-Hypopnea Index)

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Calculate your Apnea-Hypopnea Index (AHI) from apnea and hypopnea counts over total sleep hours, with AASM severity category shown instantly.

Reviewed by the thecalcu.com team · Last updated July 20, 2026

Apnea Events
0300
Hypopnea Events
0300
Total Sleep Time
hrs
112

These counts typically come from a sleep study (polysomnography) or home sleep apnea test report.

AHI

0events/hr

Severity

—

For informational purposes only. AHI severity should be interpreted by a qualified sleep medicine provider alongside your full sleep study.

What is a AHI Calculator?

An AHI Calculator computes the Apnea-Hypopnea Index, the average number of apnea and hypopnea breathing events per hour of sleep, from your total apnea count, hypopnea count, and total sleep time. It then applies the American Academy of Sleep Medicine (AASM) severity bands to classify the result as normal, mild, moderate, or severe.

AHI is the central number reported on a sleep study, and understanding exactly how it's calculated, and what severity band it falls into, makes it easier to interpret a sleep study report or track changes across repeat testing.

Why Use an AHI Calculator?

Sleep study reports list raw apnea and hypopnea counts alongside total sleep time, but translating those numbers into the single AHI figure and its severity category takes an extra calculation step. This calculator does that instantly, so you can quickly see where your result falls relative to the standard severity thresholds.

It's also useful for understanding how changes in event counts or sleep duration, from repeat testing or treatment follow-up, shift the AHI and its severity classification.

Who Should Use This Calculator?

  • Anyone reviewing a sleep study or home sleep apnea test report that lists raw apnea and hypopnea counts.
  • People following up after starting sleep apnea treatment, comparing AHI values across studies.
  • Healthcare and sleep medicine students learning how AHI is calculated and classified.
  • Anyone curious about the relationship between breathing events and sleep apnea severity, alongside tools like the Epworth Sleepiness Scale Calculator.

This calculator is for informational and educational purposes only and does not replace a sleep study or a clinical diagnosis. Sleep apnea should always be diagnosed and managed by a qualified sleep medicine provider.

What Insights Does the AHI Calculator Give You?

  • AHI, the primary result, the average number of apnea and hypopnea events per hour of sleep.
  • Severity, where that AHI falls among AASM severity bands: normal, mild, moderate, or severe sleep apnea.

Because AHI combines two event counts and a sleep duration into a single rate, seeing the calculation broken down helps clarify exactly how the reported number in a sleep study was derived.

How to use this AHI Calculator calculator

  1. Locate your Apnea Events and Hypopnea Events counts from a sleep study report.
  2. Enter the Total Sleep Time in hours, as recorded by the sleep study (not total time in bed).
  3. Review the AHI result, shown as events per hour.
  4. Check the Severity classification based on AASM thresholds.
  5. Discuss the result alongside the rest of your sleep study findings with a qualified sleep medicine provider.
Show formula & methodology ↓Show less ↑

Formula & Methodology

AHI (events/hour) = (Total Apneas + Total Hypopneas) ÷ Total Sleep Hours

Severity bands follow AASM (American Academy of Sleep Medicine) scoring criteria: normal is below 5 events/hour, mild is 5 to under 15, moderate is 15 to under 30, and severe is 30 or more.

Worked example: for 20 apnea events, 20 hypopnea events, and 7 hours of total sleep time: AHI = (20 + 20) ÷ 7 = 5.7 events/hour, which falls in the mild sleep apnea range.

Frequently Asked Questions

What is the Apnea-Hypopnea Index (AHI)?
The Apnea-Hypopnea Index (AHI) is the average number of apnea (complete breathing pauses) and hypopnea (partial breathing reductions) events per hour of sleep, recorded during a sleep study. It is the primary metric used to diagnose and grade the severity of obstructive sleep apnea.
What counts as an apnea versus a hypopnea?
An apnea is a near-complete or complete pause in airflow lasting at least 10 seconds, while a hypopnea is a partial reduction in airflow of at least 30% lasting 10 seconds or more, typically accompanied by a drop in oxygen saturation or an arousal from sleep. Sleep study reports typically list both counts separately before combining them into the AHI.
What AHI ranges indicate different severities of sleep apnea?
Under the American Academy of Sleep Medicine (AASM) criteria, an AHI below 5 is considered normal, 5 to under 15 indicates mild sleep apnea, 15 to under 30 indicates moderate sleep apnea, and 30 or higher indicates severe sleep apnea. This calculator applies those exact thresholds to your entered AHI.
Where do apnea and hypopnea counts come from?
These counts come from an overnight sleep study, either an in-lab polysomnography or a home sleep apnea test, which monitors breathing patterns, oxygen levels, and other signals throughout the night. The total counts and total sleep time are typically summarized in the sleep study report.
Why does total sleep time matter in the AHI calculation, not total time in bed?
AHI is defined per hour of actual sleep, not per hour spent in bed, because breathing events are being counted during sleep specifically. Using total time in bed instead of total sleep time would understate the true event rate, since people are typically awake for some portion of time in bed.
Is AHI the only measure used to diagnose sleep apnea?
While AHI is central to diagnosis, clinicians also consider oxygen desaturation levels, symptoms like excessive daytime sleepiness, and other findings from the sleep study when making a full diagnosis and treatment recommendation. AHI alone doesn't capture the complete clinical picture.
Can AHI vary from night to night for the same person?
Factors like sleep position, alcohol intake, nasal congestion, and sleep stage distribution can all affect AHI on any given night, which is why a single sleep study is treated as a representative sample rather than an absolute, unchanging number. Some people are also diagnosed using multi-night home testing to account for this variability.
How is sleep apnea typically treated based on AHI severity?
Mild sleep apnea may be managed with lifestyle changes, positional therapy, or an oral appliance, while moderate to severe sleep apnea more often calls for continuous positive airway pressure (CPAP) therapy. Treatment decisions depend on symptoms, AHI severity, and other health factors, and should be guided by a qualified sleep medicine provider.
How does AHI relate to daytime sleepiness?
Higher AHI is generally associated with more fragmented sleep and greater daytime sleepiness, though the relationship isn't perfectly linear for every individual. The [Epworth Sleepiness Scale Calculator](/epworth-sleepiness-scale-calculator/) measures daytime sleepiness directly and is often used alongside AHI to build a fuller picture.
Does untreated sleep apnea have long-term health risks?
Yes, untreated moderate to severe sleep apnea is associated with increased risk of high blood pressure, heart disease, stroke, and daytime accidents due to sleepiness. This makes accurate diagnosis and appropriate treatment an important health priority, guided by a qualified healthcare provider.
Can this calculator diagnose sleep apnea?
No, this calculator only performs the AHI arithmetic and applies the standard AASM severity bands to counts you already have from a sleep study. It cannot replace a sleep study itself or a clinical diagnosis, which should always come from a qualified sleep medicine provider.
Also known as
apnea hypopnea index calculatorAHI sleep study calculatorsleep apnea severity calculatorAHI score calculatorobstructive sleep apnea index