PM2.5 to US AQI Calculator (2024 EPA Scale)

PM2.5 to US AQI Calculator

Enter a 24-hour PM2.5 reading in µg/m³ to get the US AQI and its category. Many air quality apps show this US number, which is not the same as Malaysia's API.

Source: US EPA – Reconsideration of the PM NAAQS (2024 AQI breakpoints), Federal Register ↗ · IQAir – 2024 update to the US EPA Air Quality Index ↗

This result is an estimate only. Check with your bank or the relevant authority before making decisions.

Live air quality

City

This is a satellite and model estimate for the chosen city, not a station reading. It can differ from the DOE's official API. The AQI is worked out from the latest hour's PM2.5, not a 24-hour average.

Check the DOE's official API ↗ · Air quality data by Open-Meteo.com(CC BY 4.0)

How it is calculated

The reading is cut to one decimal place, then placed in a band and interpolated:

AQI = (AQI high − AQI low) ÷ (concentration high − concentration low) × (concentration − concentration low) + AQI low

PM2.5 (µg/m³)	AQI	Category
0–9.0	0–50	Good
9.1–35.4	51–100	Moderate
35.5–55.4	101–150	Unhealthy for Sensitive Groups
55.5–125.4	151–200	Unhealthy
125.5–225.4	201–300	Very Unhealthy
225.5–325.4	301–500	Hazardous

The result is rounded to a whole number and stops at 500. To see what a PM2.5 level means in cigarettes, use the haze cigarette equivalent calculator. For Malaysia’s own scale, use the haze API checker.

Worked example

PM2.5 of 100 µg/m³ is in the 55.5–125.4 band:

(200 − 151) ÷ (125.4 − 55.5) × (100 − 55.5) + 151 = 182
That is in the Unhealthy category

Why your number may differ

Apps may use the older pre-2024 table, a different averaging time, or a correction for their own sensors. This calculator covers PM2.5 only, while an AQI reported for a place is the highest of several pollutants. Malaysia’s API is a separate index. This is general information, not medical advice.

Frequently asked questions

Is the US AQI the same as Malaysia's API?

No. They use different scales and different breakpoints, so the same air can have different numbers. Malaysia's API is published by the Department of Environment. Use the haze API checker for API categories.

Why did the AQI for the same PM2.5 change in 2024?

The US EPA tightened its PM2.5 breakpoints in May 2024. The Good category now ends at 9.0 µg/m³ instead of 12.0, and the upper bands were rescaled. Apps that still use the old table will show different numbers.

Which PM2.5 average should I use?

The AQI is defined for a 24-hour average. A single hour's reading gives a rough idea only.