😴 AHI Calculator

The apnea-hypopnea index is the headline number of every sleep study: the average number of times per hour your breathing pauses (apneas) or drops significantly (hypopneas) while you sleep. Under 5 events per hour is normal. Above 30 is severe. Everything about sleep apnea diagnosis and treatment flows from this one number.

If your sleep report lists total apneas, total hypopneas, and total sleep time, this calculator turns them into your AHI and explains the severity band. It also explains why the number alone never tells the whole story.

How to use this calculator

Find the three numbers on your polysomnography or home sleep test report: total apneas, total hypopneas, and total sleep time in hours.

The formula and severity bands

AHI is simply events divided by hours of sleep. Both apneas and hypopneas count equally in the standard definition.

These cutoffs come from the American Academy of Sleep Medicine and are used worldwide. Note the boundaries: an AHI of 14.9 is mild and 15.0 is moderate, which looks arbitrary because it partly is. Clinicians treat the patient, not the decimal.

Worked example

A sleep study records 45 apneas and 60 hypopneas over 7 hours of sleep. AHI = (45 + 60) / 7 = 105 / 7 = 15.0 events per hour. That lands exactly on the moderate threshold. With daytime sleepiness or hypertension, this patient would typically be offered CPAP.

Contrast 12 apneas and 18 hypopneas over 6.5 hours: AHI = 30 / 6.5 = 4.6, normal. But if this person falls asleep at red lights, the normal AHI does not end the story: other disorders like narcolepsy or insufficient sleep need evaluation.

What your result means

Normal (under 5): no sleep apnea by the numbers. Mild (5 to 15): treatment hinges on symptoms and risk factors; options range from positional therapy and oral appliances to CPAP. Moderate (15 to 30): CPAP is usually recommended, particularly with sleepiness, hypertension, or cardiac disease. Severe (30+): treatment is strongly advised given the links to stroke, heart failure, and arrhythmia.

Two caveats: home sleep tests can underestimate AHI because they measure recording time rather than true sleep time, and AHI does not capture how deep your oxygen drops, which also matters. For better sleep habits overall, our sleep cycle calculator plans bedtimes around 90-minute cycles, and the sleep debt calculator tracks what you owe yourself.

Beyond the number

Sleep physicians increasingly look past AHI at the hypoxic burden: how far and how long oxygen saturation falls. Two people with an AHI of 20 can have very different oxygen profiles, and the one with deeper desaturations likely carries more cardiovascular risk. Newer reports include this metric, and it is worth asking about.

Positional and REM-specific apnea also matter. Some people have an AHI of 30 on their back and 5 on their side; others only obstruct in REM sleep. These patterns change treatment: positional therapy works for the first group and not the second. Your full report has these details even when the headline number does not.

Treatment options by severity

CPAP remains the gold standard across moderate and severe apnea and for symptomatic mild cases. Modern machines are quiet, auto-adjusting, and far less intrusive than the devices of twenty years ago; the main barrier is consistently mask fit, which is solvable with a good equipment provider and a week of patience.

Alternatives have real roles. Custom mandibular advancement devices from a dentist help mild to moderate apnea, especially in people who cannot tolerate CPAP. Positional therapy (keeping off the back) works when apnea is strongly position-dependent. Weight loss of 10 percent or more can drop AHI meaningfully, and treating nasal congestion improves CPAP tolerance.

Surgery, from tonsillectomy in selected adults to hypoglossal nerve stimulation implants, is reserved for specific anatomies after sleep-surgery evaluation. Whatever the route, success is measured the same way: a repeat study showing AHI under 5 and, what matters more, days that feel different.

Why AHI varies night to night

Repeat sleep studies on the same person often differ by 5 to 10 events per hour, enough to cross a severity boundary. Alcohol is the biggest single-night raiser: it relaxes airway muscles and fragments sleep, and one study night after drinking can inflate AHI substantially. Back-sleeping does the same for positional apnea, sometimes tripling the number versus side-sleeping.

Nasal congestion from a cold or allergies raises airway resistance and nudges events upward, while REM-heavy nights score worse because apnea concentrates in REM sleep. First-night effect matters too: sleeping badly in a strange lab bed with wires attached can either raise AHI (fragmented sleep) or lower it (less REM).

Clinicians account for this by treating borderline results with judgment and repeating studies when the number and the symptoms disagree. Home tests spread over multiple nights are gaining ground partly for this reason: three typical nights beat one unusual one.

For informational purposes only, not medical advice. Consult a healthcare professional.