AQI Calculator

Convert a pollutant concentration into the US EPA Air Quality Index. Pick a pollutant (PM2.5, PM10, ground-level ozone, carbon monoxide, nitrogen dioxide or sulphur dioxide), enter the measured concentration, and get the AQI value, its category with the official colour band, and the corresponding health advisory. The ozone entry offers the EPA's 8-hour and 1-hour scales. The AQI is computed by piecewise-linear interpolation across the EPA breakpoint table. Everything runs locally in your browser.

Pollutant

Concentration

8-hour average 1-hour average

Reference: US EPA AQI breakpoint tables (Technical Assistance Document). AQI = (I_hi − I_lo)/(C_hi − C_lo)·(C − C_lo) + I_lo, rounded. The overall daily AQI reported by agencies is the maximum of all pollutant sub-indices — compute each pollutant here and take the highest.