What Is AHI? The Key Metric for Sleep Apnea
The Apnea‑Hypopnea Index, or AHI, is the number you will see at the top of your sleep study report. It represents the average number of breathing pauses — apneas (complete stops) and hypopneas (partial reductions) — you experience per hour of sleep. This single number determines whether you have obstructive sleep apnea and, if so, how severe it is. When people search for an AHI calculator or an apnea hypopnea index calculator, they usually want to calculate AHI from sleep study data quickly, without waiting for their follow‑up appointment. Our tool does exactly that: plug in the numbers from your report and see where you fall on the severity scale.
| Metric | Definition |
|---|---|
| Apnea | Complete cessation of airflow for ≥ 10 seconds |
| Hypopnea | Partial reduction of airflow (≥30%) with oxygen desaturation or arousal |
| AHI | (Apneas + Hypopneas) ÷ total sleep hours |
Based on AASM Scoring Manual Version 3.0.
How to Calculate Your AHI
The formula is straightforward: add the total number of apneas and hypopneas recorded during your sleep study, then divide by the total number of hours you actually slept (not time in bed). For example, if your report shows 80 apneas and 40 hypopneas over 7 hours of sleep, your AHI is (80 + 40) / 7 = 17.1 — which falls in the moderate range. Our AHI calculator does the math for you, and also explains what your score means. A low CPAP AHI reading (typically under 5) is the goal of therapy.
| AHI range | Severity | Health implications |
|---|---|---|
| 0 – 4.9 | Normal | No sleep apnea |
| 5 – 14.9 | Mild | May cause daytime sleepiness; associated with hypertension risk |
| 15 – 29.9 | Moderate | Increased cardiovascular risk; CPAP often recommended |
| 30+ | Severe | Significant health risks; urgent treatment indicated |
American Academy of Sleep Medicine International Classification of Sleep Disorders.
What the AHI Severity Levels Really Mean
If you are curious about what is a good AHI score, the answer is under 5. AHI values between 5 and 15 indicate mild sleep apnea, which may be managed with positional therapy, oral appliances, or lifestyle changes. Values between 15 and 30 are moderate, and CPAP is typically the first‑line treatment. AHI above 30 is severe, and treatment becomes especially important to reduce the strain on your heart and brain. The AHI severity chart above is the standard reference, but remember: AHI is just one metric. Your sleep physician will also consider your oxygen saturation nadir, arousal index, and symptoms.
| Population | Average AHI |
|---|---|
| Healthy young adults | 0.5 – 2.0 |
| Overweight adults (BMI 25‑30) | 3 – 10 |
| Obese adults (BMI >30) | 10 – 30+ |
| Elderly (>65 years) | 5 – 15 (may be "age‑normal") |
Source: Bixler et al., 1998; AASM data.
CPAP Therapy and Your AHI
Once you start CPAP, many machines display a residual CPAP AHI reading each morning. This shows how many events you experienced while using the mask. A well‑adjusted CPAP should bring your AHI below 5 — ideally below 2. If your CPAP AHI remains high, you may need a mask adjustment, a pressure change, or evaluation for other issues. Keep a log of your nightly AHI and discuss trends with your provider.
| Baseline AHI | CPAP AHI goal | Meaning |
|---|---|---|
| 15 | < 5 | Effective therapy |
| 30 | 5 – 10 | Partial improvement; may need adjustment |
| 50 | > 10 | Inadequate treatment; consult provider |
| Health outcome | Increased risk |
|---|---|
| Hypertension | 2 – 3x |
| Coronary artery disease | 2x |
| Stroke | 2 – 3x |
| Type 2 diabetes | 1.5 – 2x |
Based on Young et al., 2008; Marin et al., 2005.
Frequently Asked Questions
- American Academy of Sleep Medicine. (2023). AASM Manual for the Scoring of Sleep and Associated Events.
- Young, T., et al. (2008). Epidemiology of obstructive sleep apnea: a population health perspective. American Journal of Respiratory and Critical Care Medicine.
- Marin, J. M., et al. (2005). Long‑term cardiovascular outcomes in men with obstructive sleep apnoea. The Lancet.
- Bixler, E. O., et al. (1998). Effects of age on sleep apnea in men. American Journal of Respiratory and Critical Care Medicine.