# The AQI Equation **URL:** https://forum.airnowtech.org/t/the-aqi-equation/169 **Category:** Air Quality and AQI Info **Created:** [July 5, 2016, 10:37pm UTC](https://forum.airnowtech.org/t/the-aqi-equation/169 "2016-07-05T22:37:42Z") **Posts on this page:** 1 **Page:** 1
### Author: ![mwhylton](https://forum.airnowtech.org/user_avatar/forum.airnowtech.org/mwhylton/32/21_2.png) [@mwhylton](https://forum.airnowtech.org/u/mwhylton) #### Post date: [July 5, 2016, 10:37pm UTC](https://forum.airnowtech.org/t/the-aqi-equation/169/1 "2016-07-05T22:37:44Z")
## AQI Equation ![](https://forum.airnowtech.org/uploads/default/original/1X/e4311a157854cfade9e39b8eaacc41aba85d43bb.PNG) Where Conci = Input concentration for a given pollutant ConcLo = The concentration breakpoint that is less than or equal to Conci ConcHi = The concentration breakpoint that is greater than or equal to Conci AQILo = The AQI value/breakpoint corresponding to ConcLo AQIHi = The AQI value/breakpoint corresponding to ConcHi ## Rounding vs. Truncating For all AQI calculations, the **calculated average concentrations are truncated** to .001 ppm (1 ppb) for O3, 0.1 μg/m3 for PM2.5, and 1 μg/m3 for PM10. This truncated concentration is then used as the input (Conci) in the AQI equation above. The resulting **AQI is rounded** to the nearest whole number. ## AQI and Concentration Breakpoints by Pollutant ![Equation2](https://forum.airnowtech.org/uploads/default/original/1X/59ab0522bc2fd508e6fcbc1b41431d5069aef1be.png) ![Equation3](https://forum.airnowtech.org/uploads/default/original/1X/d7f67d77814e465e13c665b2fc1d0dd73ddae1d4.png) ![](https://forum.airnowtech.org/uploads/default/original/1X/86f96b612020bc83b5f0d8c9b3c57e0a27c173d9.PNG) AQI values above 500 are considered Beyond the AQI. Follow recommendations for the Hazardous category. Additional information on reducing exposure to extremely high levels of particle pollution is available [here](https://www.airnow.gov/aqi/aqi-basics/extremely-high-levels-of-pm25/).