My AQIAQI calculator
Turn a PM2.5, PM10 or ozone reading into the US Air Quality Index (AQI) and see what it means for your health.
No reading? Get the live AQI around you
This calculator needs a number. My AQI gets it for you, from the monitoring station closest to you.
- Live AQI, PM2.5, PM10, ozone, NO2, SO2 and CO
- Any city, and your saved places
- Premium: full sensor map, Home Screen and Lock Screen widgets, no ads
Free on iPhone and iPad, with optional Premium.
AQI categories
| AQI | Category | PM2.5 (µg/m³) | PM10 (µg/m³) | Ozone 8-h (ppb) |
|---|
Frequently asked questions
How is the AQI calculated from PM2.5?
The concentration is truncated to one decimal and placed in its EPA breakpoint range (for example 9.1–35.4 µg/m³ for Moderate). The AQI is then interpolated linearly inside that range and rounded to the nearest whole number. A PM2.5 of 35.4 µg/m³ gives an AQI of 100.
What is a good AQI?
0 to 50 is Good and 51 to 100 is Moderate. Above 100, people in sensitive groups, such as those with asthma, children and older adults, should start limiting long or intense time outdoors.
Why did the PM2.5 thresholds change in 2024?
In 2024 the US EPA tightened the annual PM2.5 standard and lowered the top of the Good range from 12.0 to 9.0 µg/m³, so the same reading can now show a higher AQI than before. Some data providers have not switched yet, so their numbers can differ slightly from this calculator.
Which pollutant sets the overall AQI?
Each pollutant gets its own index; the overall AQI is the highest of them, and that pollutant is called the dominant pollutant.
Is this the same AQI as other countries use?
No. This is the US EPA scale, which many apps use worldwide. Countries such as India, China, Canada and the UK publish their own indices with different thresholds.
This calculator uses the US EPA AQI breakpoints updated in 2024 (40 CFR Part 58, Appendix G). Readings are truncated as EPA specifies before the index is calculated. It runs entirely in your browser; nothing you type is sent anywhere. For information only; not medical advice.