Air Quality Index Calculator (US EPA PM2.5)
Convert a PM2.5 concentration (µg/m³) to the US EPA Air Quality Index and health category.
How to Use the Air Quality Index Calculator (US EPA PM2.5)
- Get a 24-hour average PM2.5 reading in µg/m³.
- Enter it in the field.
- Click Calculate to see AQI and health category.
حالات الاستخدام
- •Daily air-quality reporting.
- •Outdoor activity planning.
- •Teaching environmental science.
الصيغة
I = ((I_hi − I_lo) / (BP_hi − BP_lo)) × (C − BP_lo) + I_lo, applied piecewise to the PM2.5 breakpoints.
الأسئلة الشائعة
What is PM2.5?
Fine particulate matter with aerodynamic diameter under 2.5 µm. Small enough to reach the alveoli and cross into the bloodstream.
Why the 2024 revision?
EPA tightened the annual NAAQS to 9 µg/m³ in 2024. The 24-hour breakpoints in this calculator match the current AQI table used on AirNow.
Is this the same as CAQI or CAI?
No — European CAQI and Korean CAI use different breakpoints. Always use the scale published by the regulator whose air you are describing.