Air Quality Index (AQI) Calculator
Check real-time global Air Quality Index (AQI), PM2.5, and health advisories for any city.
How It Works & Educational Guide
How To Use
- Type the name of any city in the search bar.
- Click the search button and wait a second for the tool to fetch live Open-Meteo data.
- Review your local AQI score, health advisory label, and detailed PM2.5 / PM10 readings.
How the Index Works
Index ranges from 0-500. Green (0-50) is Good, Red (151-200) is Unhealthy, and Maroon (301+) is Hazardous.
What the results mean
A PM2.5 reading of 60 µg/m³ correlates to an Unhealthy AQI of roughly 150, prompting a warning to restrict outdoor exercise.
Frequently Asked Questions
What is the Air Quality Index (AQI)?
The Air Quality Index (AQI) is a standard measurement used by environmental agencies to communicate how polluted the air currently is or how polluted it is forecast to become. It translates complex concentration levels of various pollutants into a single number on a scale from 0 to 500, making it easier for the general public to understand the health risks associated with the air they are breathing.
Why should I track PM2.5 levels?
PM2.5 refers to fine particulate matter with a diameter of 2.5 micrometers or less. These particles are so small they can penetrate deep into the lungs and even enter the bloodstream. High PM2.5 levels are linked to significant health issues, including asthma, heart disease, and reduced lung function. Keeping track of PM2.5 is crucial for protecting your cardiovascular and respiratory health.
What do the AQI colors mean?
AQI values are divided into six color-coded categories corresponding to different levels of health concern. Green (Good, 0-50) indicates little to no risk. Yellow (Moderate, 51-100) is acceptable but may affect unusually sensitive people. Orange (Unhealthy for Sensitive Groups, 101-150) warns vulnerable populations. Red (Unhealthy, 151-200) indicates everyone may experience health effects. Purple (Very Unhealthy, 201-300) and Maroon (Hazardous, 301+) trigger health alerts for the entire population.
How often is the Air Quality Data updated?
Our tool fetches live data directly from the Open-Meteo Air Quality APIs, which aggregate data from global weather models and monitoring stations. The data is typically updated hourly, ensuring you have the most current information possible when planning outdoor activities or deciding whether to open your windows.
Is this calculator entirely free to use?
Yes, the Air Quality Index Calculator is completely free to use. We rely on open-source and free-tier APIs to bring this vital environmental data directly to your device without any cost or subscription requirements, aligning with our mission to provide accessible, high-value tools to everyone.
Reviewed by Lion Health Team · Updated July 23, 2026