Key facts
- Each pollutant concentration is converted to its own sub-index.
- The highest valid sub-index becomes the estimated overall AQI.
- PM values use µg/m³; ozone and CO use ppm; NO₂ and SO₂ use ppb.
- An instantaneous reading is not equivalent to an official AQI reporting average.
Interactive tool
Estimate US AQI
Estimated overall US AQI
—Enter at least one concentration to calculate.Estimate only. Official AQI reporting applies pollutant-specific averaging, data quality and reporting rules that this concentration converter cannot verify.
How the calculation works
The calculator truncates or rounds pollutant inputs as required by the breakpoint table, identifies the concentration interval and applies linear interpolation to obtain the pollutant sub-index.
When several pollutants are entered, the largest calculated sub-index is reported as the estimated overall AQI and that pollutant is identified as dominant.
Units and averaging periods
| Pollutant | Calculator unit |
|---|---|
| PM2.5 | µg/m³ |
| PM10 | µg/m³ |
| Ozone | ppm |
| Carbon monoxide | ppm |
| Nitrogen dioxide | ppb |
| Sulfur dioxide | ppb |
Frequently asked questions
Why is my result different from an air-quality app?
The app may use an official reporting average, a different station, updated data, nowcast logic or another national AQI standard.
Can I calculate India CPCB AQI here?
No. This calculator uses US EPA breakpoints. India CPCB AQI has different breakpoints and calculation requirements.
What happens if I enter several pollutants?
The calculator estimates a sub-index for each valid entry and reports the highest as the overall AQI.
Sources
This reference was prepared from the following primary public-health and regulatory sources:
- Technical Assistance Document for the Reporting of Daily Air QualityUnited States Environmental Protection Agency
- Patient Exposure and the Air Quality IndexUnited States Environmental Protection Agency