PM2.5 to AQI converter
Convert fine-particle pollution between µg/m³ and air quality index values, and see what a day of it is like.
That's 1.17× as polluted as a polluted city day, while a heavy smog day is 2.9× more polluted. On the US index that is AQI 99: moderate.
What it means
How dirty is that air?
For 24-hour averages of PM2.5 only. Official AQI values take the worst of several pollutants; hourly readings shown by apps are estimates.
Every unit
That air in every scale
Learn
Three things worth knowing
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22 µg/m³ is one cigarette
Breathing 22 µg/m³ of PM2.5 for a day harms the body about as much as smoking one cigarette (Berkeley Earth, 2015).
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From PSI to AQI
The US Pollutant Standards Index of 1976 became the AQI in 1999, when PM2.5 was added. Other countries copied the 0–500 idea with their own breakpoints.
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AQI is not µg/m³
An AQI of 100 means 35.4 µg/m³ in the US scale but 75 µg/m³ in China’s; always check which scale an app uses.
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Popular air pollution conversions
Background
About PM2.5 and the AQI
PM2.5 are particles under 2.5 micrometers, fine enough to reach the lungs and the blood. They are measured in micrograms per cubic meter of air. The WHO advises a yearly average under 5 µg/m³ and a daily one under 15.
An air quality index turns that into a 0–500 score with colored bands. The US EPA lowered its breakpoints in 2024: AQI 50 is now 9 µg/m³, AQI 100 is 35.4.