Air Quality Index (AQI) Health Calculator

Enter a pollutant type and its concentration level to calculate the corresponding Air Quality Index (AQI) score using the US EPA standard. The AQI Health Calculator returns your AQI value, AQI category (Good through Hazardous), color code, sensitive groups at risk, health effects, and cautionary statements — so you know exactly what the air quality means for your health.

Choose the pollutant you want to convert to AQI.

Enter the measured concentration of the selected pollutant.

Results

AQI Value

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AQI Category

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Concentration Unit

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Sensitive Groups

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Health Effects

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Cautionary Statement

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AQI Score vs. Category Thresholds

Results Table

Frequently Asked Questions

What is the Air Quality Index (AQI)?

The AQI is a standardized index developed by the US EPA to communicate how clean or polluted outdoor air is and what associated health effects might be of concern. It runs from 0 to 500 — the higher the number, the greater the level of air pollution and health risk. Six color-coded categories range from 'Good' (0–50) to 'Hazardous' (301–500).

Which pollutants are included in the AQI calculation?

The US EPA AQI covers five major pollutants regulated by the Clean Air Act: ground-level ozone (O₃), particle pollution (PM2.5 and PM10), carbon monoxide (CO), sulfur dioxide (SO₂), and nitrogen dioxide (NO₂). Each pollutant has its own concentration-to-AQI breakpoints, and the overall AQI for an area is the highest single-pollutant AQI at that time.

What are the six AQI categories and what do they mean?

The six AQI categories are: Good (0–50, minimal risk), Moderate (51–100, acceptable but some sensitive people may be affected), Unhealthy for Sensitive Groups (101–150, sensitive individuals should limit prolonged outdoor exertion), Unhealthy (151–200, everyone may begin to experience health effects), Very Unhealthy (201–300, health alert — everyone may experience serious effects), and Hazardous (301–500, emergency conditions affecting the entire population).

Who are considered 'sensitive groups' for air quality?

Sensitive groups vary by pollutant but generally include people with lung diseases such as asthma or COPD, people with heart or cardiovascular disease, children and teenagers, older adults, and people who are active outdoors. On high-AQI days, these groups are advised to reduce or avoid prolonged outdoor physical activity before the general public.

How is the AQI mathematically calculated from a concentration?

The EPA uses a piecewise linear formula: AQI = ((AQI_high - AQI_low) / (C_high - C_low)) × (C - C_low) + AQI_low, where C is the measured concentration and the high/low values come from the EPA breakpoint tables for each pollutant. This calculator applies those exact EPA breakpoints for PM2.5, PM10, O₃, CO, SO₂, and NO₂.

What is an Air Quality Action Day?

An Air Quality Action Day is declared by local air agencies when the AQI is forecast to exceed 100 — the 'Unhealthy for Sensitive Groups' threshold. On these days, sensitive individuals are urged to limit outdoor activity, schools may cancel outdoor sports, and the public is encouraged to reduce activities that contribute to pollution such as driving or using gas-powered equipment.

Is PM2.5 more dangerous than PM10?

Yes, PM2.5 (fine particles smaller than 2.5 micrometers) is generally considered more hazardous than PM10 because the tiny particles can penetrate deep into the lungs and even enter the bloodstream, causing respiratory and cardiovascular problems. PM10 particles are larger and mostly filtered in the upper airways, though both are regulated and tracked in the AQI.

Can I use this calculator for real-time air quality decisions?

This calculator converts a known concentration value into an AQI score using official EPA breakpoints — it is accurate for that conversion. For real-time, location-based air quality data, check airnow.gov or a local air quality monitoring agency, which pull from live sensor networks and official monitoring stations.

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