# Daily and Hourly AQI - Ozone

**URL:** https://forum.airnowtech.org/t/daily-and-hourly-aqi-ozone/170
**Category:** Ozone
**Created:** [July 5, 2016, 10:48pm UTC](https://forum.airnowtech.org/t/daily-and-hourly-aqi-ozone/170 "2016-07-05T22:48:18Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### 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, 10:48pm UTC](https://forum.airnowtech.org/t/daily-and-hourly-aqi-ozone/170/1 "2016-07-05T22:48:18Z")

</div>

## Daily Ozone AQI

The daily ozone AQI is calculated by taking the maximum 8 hour concentration from 07:00-23:00 LST, and then converting to AQI. Each 8-hour average concentration is truncated to .001ppm/1ppb. There are 17 8-hour averages considered in each day. Each 8-hour average requires 6 of 8 hours (75%) for a valid calculation. In addition, 75% or 13/17 of the 8-hour averages are needed for a valid daily ozone AQI calculation.

 ![](https://forum.airnowtech.org/uploads/default/original/1X/18e3359f557d938ec6e9e0724ea72b2b85be7740.PNG)

Example 1: Valid

 ![](https://forum.airnowtech.org/uploads/default/original/1X/0a4a8210dc41697f4f34f8caf3fcae99fdffb606.PNG)

Example 2: Valid with Missing Data (Red background/text= invalid or missing)

 ![](https://forum.airnowtech.org/uploads/default/original/1X/de2e54e49ed1680d69788f6f5c6fd22a1ed12a07.PNG)

Example 3: Insufficient Data (Red background/text= invalid or missing)

 ![](https://forum.airnowtech.org/uploads/default/original/1X/da06d7e85d2cd59aa906d329c9a5f9d3ef003f4f.PNG)

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## Hourly Ozone AQI

### NowCast AQI method

For real-time and other hourly readings, the NowCast method is used to calculate the AQI for each hour. In 2021, the NowCast also replaced the midpoint averaging method (described below) for hourly AQI from older hours. For information on how to calculate the NowCast for Ozone, click [here](https://forum.airnowtech.org/t/the-nowcast-for-ozone-2019-update-partial-least-squares-method/356).