Air Quality Calculators
Plain, no-account, no-tracking calculators for the math that actually comes up when you're trying to decide whether to go for a run, what air purifier to buy, or how to read a number on a monitor.
AQI Calculator
Convert a PM2.5, PM10, ozone, NO₂, SO₂, or CO concentration to the U.S. EPA Air Quality Index value, category, and color. Built on the official 2024 breakpoints, including the February 2024 PM2.5 NAAQS revision.
Open calculator →Air Purifier Sizing Calculator
Enter your room dimensions and pick a use case — everyday air, allergies, or wildfire smoke. Get the minimum CADR (Clean Air Delivery Rate) your purifier needs, with a sensible derating for real-world conditions.
Open calculator →Why these specific calculators
Most online "AQI calculators" don't show their breakpoints, haven't been updated for the 2024 EPA standard change, or quietly use the wrong averaging period. Most air-purifier "calculators" tell you which unit to buy from their affiliate link, not what CADR you actually need. We wanted plain math, plain sources, no upsell.
If you'd rather just look at the live number for your area, the Smog Report iOS app pulls it from EPA AirNow directly — free, no account.
Get real-time AQI on iPhone
Smog Report pulls live AQI worldwide. Free, no account, with widgets and Live Activities.
Download for iOS