Updated Environment & Weather

Air Quality Index (AQI) Calculator

Compute air quality using US AQI and European CAQI, convert PM2.5 to AQI and get clear health guidance. Enter raw pollutant concentrations or ready-made AQI values and see the overall category and color scale.

US EPA AQI European CAQI PM2.5 ↔ AQI Converter AQI Color & Health Guide

Interactive Air Quality Index (AQI) Calculator

Use the tabs to calculate US AQI from pollutant concentrations, combine AQI values from different sources, convert PM2.5 to AQI, estimate European CAQI and explore health guidance based on the AQI category.

Enter the latest 24-hour average for particulate matter and appropriate averaging periods for gases. The calculator applies standard US EPA breakpoint formulas to estimate individual pollutant AQIs and the overall US AQI.

Use this mode when your air quality device or API already reports pollutant-specific AQIs. The overall AQI is simply the highest of the individual AQIs, and the dominant pollutant is the one that produces it.

This quick converter uses the US EPA breakpoint table for PM2.5. When converting from AQI back to concentration, the result is an approximate value within the corresponding breakpoint band.

This simplified CAQI mode uses typical European breakpoints for urban background monitoring. The final CAQI is the maximum of the sub-indices for PM, NO₂ and ozone.

Use this tab to interpret any AQI value, whether it comes from this calculator, a monitoring network or a mobile app.

US AQI Color Scale

AQI range Category Color Typical guidance
0 – 50 Good Green Air quality is considered satisfactory; little or no risk.
51 – 100 Moderate Yellow Acceptable air quality, but some pollutants may be a concern for a very small number of unusually sensitive people.
101 – 150 Unhealthy for Sensitive Groups Orange Members of sensitive groups may experience health effects; the general public is not likely to be affected.
151 – 200 Unhealthy Red Everyone may begin to experience health effects; members of sensitive groups may experience more serious effects.
201 – 300 Very Unhealthy Purple Health alert: everyone may experience more serious health effects.
301 – 500 Hazardous Maroon Health warnings of emergency conditions; the entire population is more likely to be affected.

Air Quality Index (AQI) Calculator – US AQI, CAQI and PM2.5 Tools in One Place

Air quality affects health, comfort and outdoor planning just as much as temperature and humidity. The Air Quality Index (AQI) summarizes a group of pollutant measurements into a single number and color-coded category that is easier to understand at a glance.

This Air Quality Index Calculator from MyTimeCalculator combines several commonly used approaches in one interface. You can calculate the US AQI from raw pollutant concentrations, merge existing AQI values from sensors or APIs, convert PM2.5 between micrograms per cubic meter and AQI, and estimate a simplified European CAQI value.

US AQI from Pollutant Concentrations

In the first tab you enter measured concentrations for key pollutants such as PM2.5, PM10, ozone and carbon monoxide. For each pollutant, the US EPA defines a piecewise linear relationship between concentration and AQI using breakpoint tables. The calculator:

  • Finds the appropriate breakpoint range for each pollutant.
  • Applies the standard linear interpolation formula to compute a pollutant-specific AQI.
  • Chooses the highest of these values as the overall AQI.
  • Identifies the dominant pollutant and its category.

A results table shows concentration, pollutant AQI and category for each pollutant so you can see what is driving the overall index.

US AQI from Pollutant AQI Values

Many air quality APIs or devices already report AQI by pollutant. In that case you do not need to recompute AQI from concentrations. The second tab lets you enter those AQI values directly, then:

  • Finds the maximum across pollutants.
  • Identifies the associated pollutant as the dominant one.
  • Maps the overall AQI to a category and health message.

PM2.5 to AQI and AQI to PM2.5 Converter

Fine particulate matter (PM2.5) is often the main driver of AQI, especially during wildfire smoke events and urban pollution peaks. The PM2.5 tab provides a quick way to:

  • Convert PM2.5 concentration to its US AQI value.
  • Convert an AQI number back to an approximate PM2.5 concentration within the associated breakpoint band.
  • See the corresponding category and color.

European Common Air Quality Index (CAQI)

Outside the United States, different index systems exist. The European CAQI is one such approach that is often based on PM10, PM2.5, NO₂ and ozone. The CAQI tab in this calculator uses a simplified urban background scheme where the final CAQI is the maximum of the sub-indices for these pollutants.

AQI Health & Color Guidance

Numbers alone are not always intuitive. The health guide tab lets you enter any AQI value and returns:

  • The US AQI category name.
  • The standard color code.
  • A short summary of what the category means.
  • More detailed guidance for sensitive groups and the general population.

A reference table at the bottom of the tab summarizes all six US AQI categories and their ranges so you have everything in one place.

How to Use This AQI Calculator Effectively

  • Use the US AQI – Concentrations tab if you have raw sensor values or official reports in µg/m³ or ppm.
  • Use the US AQI – AQI Inputs tab if your device or API already gives pollutant-specific AQIs.
  • Use the PM2.5 Converter when you want a quick estimate from PM2.5 alone.
  • Use the European CAQI tab if you are comparing with European-style indices.
  • Use the Health & Color Guide to explain AQI values to non-technical users.

This tool is intended for education and planning. Regulatory agencies may use additional rules, averaging methods and quality controls, so official AQI numbers in your area may differ slightly from the calculator’s output.

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Air Quality & Health FAQs

Frequently Asked Questions About AQI and Air Quality

Get quick answers before you interpret your AQI readings or build dashboards around them.

The overall AQI is designed to reflect the worst health risk at a given time. Taking the maximum of the pollutant-specific AQIs ensures that if one pollutant is at an unhealthy level, the overall AQI reflects that, even if other pollutants are relatively low.

Yes. For both US AQI and CAQI systems, higher numbers indicate poorer air quality and a higher likelihood of health effects, especially for sensitive groups such as children, older adults and people with heart or lung disease.

Not exactly. Each system uses its own breakpoints and may include different pollutants or averaging periods. Categories and color schemes may be similar, but the same numeric value in two systems does not always indicate identical health risk.

Many harmful pollutants are not visible to the naked eye. Fine particles and gases can reach unhealthy levels without producing obvious haze, so AQI and monitoring stations are important for understanding real exposure risk.

AQI is a key factor, but personal sensitivity, duration of activity, intensity of exercise and local guidance also matter. For sensitive groups, it’s wise to follow precautionary advice when AQI reaches “Unhealthy for Sensitive Groups” or higher.

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