What PM2.5 breakpoints does this calculator use?

It uses the U.S. EPA PM2.5 AQI breakpoints that became effective on May 6, 2024: 0.0 to 9.0 for Good, 9.1 to 35.4 for Moderate, 35.5 to 55.4 for Unhealthy for Sensitive Groups, 55.5 to 125.4 for Unhealthy, 125.5 to 225.4 for Very Unhealthy, and 225.5 and above for Hazardous.

Is AQI the same in every country?

No. AQI systems and breakpoints vary by country. This page is for the U.S. AQI for PM2.5 only.

Does this calculate real-time NowCast AQI?

No. It converts one PM2.5 concentration or one AQI value. Real-time NowCast AQI uses recent hourly monitor data before the concentration is converted to an AQI.

Why does AQI 100 convert to 35.4 ug/m3?

Under the U.S. PM2.5 AQI table, AQI 100 is the upper end of the Moderate category and corresponds to 35.4 micrograms per cubic meter.

Is my air quality input uploaded?

No. The calculator runs locally in your browser and does not send entered AQI or PM2.5 values to a server.

AQI to PM2.5 Converter and Air Quality Category Checker

Convert U.S. AQI to PM2.5 concentration, or enter PM2.5 to check the AQI category. Everything runs locally in your browser.

Last updatedJune 30, 2026

Core methodEPA AQI breakpoint interpolation

BreakpointsU.S. PM2.5 AQI, effective May 6, 2024

PrivacyNo server upload or input tracking

Quick Answer

For U.S. PM2.5 AQI, AQI 50 is about 9.0 ug/m3, AQI 100 is about 35.4 ug/m3, AQI 150 is about 55.4 ug/m3, AQI 200 is about 125.4 ug/m3, AQI 300 is about 225.4 ug/m3, and AQI 500 is about 325.4 ug/m3.

FormulaAQI is linearly interpolated between the PM2.5 breakpoint pair for the category.

ScopeThis is for U.S. AQI and PM2.5 only, not ozone, PM10, or non-U.S. indices.

LimitValues above AQI 500 are outside this calculator's standard AQI table.

Inputs

AQI to PM2.5

AQI value (0 to 500) Pollutant and index

AQI is normally reported as a whole number. Decimal entries are rounded to the nearest whole AQI before conversion.

This tool does not convert PM10, ozone, carbon monoxide, sulfur dioxide, or nitrogen dioxide.

Results

Enter an AQI or PM2.5 concentration, then calculate.

How the Conversion Works

The U.S. AQI uses pollutant-specific breakpoints. For PM2.5, the calculator finds the breakpoint interval containing the value, then interpolates between the concentration range and AQI range for that category.

AQI = ((Ihi - Ilo) / (Chi - Clo)) x (C - Clo) + Ilo PM2.5 = ((AQI - Ilo) / (Ihi - Ilo)) x (Chi - Clo) + Clo C = PM2.5 concentration in ug/m3; I = AQI; Lo and Hi are the matched breakpoint bounds.

Planning limit: this is an informational converter, not medical advice or an official air monitoring result. Follow local public health alerts, AirNow, and your air agency during smoke, dust, or pollution events.

U.S. PM2.5 AQI Breakpoints

Category	AQI	PM2.5 concentration (ug/m3)	Color

Assumptions and Sources

2024 update

EPA updated the PM2.5 AQI breakpoints effective May 6, 2024. The Good category now ends at 9.0 ug/m3, and upper category breakpoints were also revised.

NowCast

AirNow can report a near real-time NowCast AQI from recent hourly monitor data. This page converts only the final AQI or concentration value you enter.

Sensor caution

Low-cost sensors can be useful for local trends, but readings may need calibration or correction before comparison with official AQI values.

References: AirNow AQI Calculator, EPA Final Updates to the AQI for Particulate Matter fact sheet, and EPA PM NAAQS final reconsideration.

FAQs

What does PM2.5 mean?

PM2.5 means fine particulate matter with diameters generally 2.5 micrometers or smaller. These particles can come from smoke, combustion, dust reactions, and other sources.

Can I convert any AQI number to PM2.5?

Only if the AQI is specifically a U.S. PM2.5 AQI. A general location AQI may be driven by ozone, PM10, or another pollutant, so it cannot always be converted to PM2.5.

Why is PM2.5 to AQI not perfectly reversible?

AQI is reported as a whole number and PM2.5 breakpoints are expressed to one decimal place. Rounding and truncation can make a round-trip conversion differ by a small amount.

What happens above AQI 500?

The public AQI table is usually presented from 0 to 500. PM2.5 above the AQI 500 concentration is still hazardous, but this calculator does not assign a precise AQI above 500.

Is this a medical safety checker?

No. It identifies the AQI category from a numeric value. Use local health guidance, official alerts, and clinician advice for health-sensitive decisions.