What smog is
Smog is a form of air pollution dominated by ground-level ozone, which forms when sunlight reacts with pollutants like vehicle and industrial emissions. It is not directly emitted but is a secondary pollutant, and it tends to be worse on hot, sunny, still days.
How this calculator works
This tool applies the U.S. EPA’s standard piecewise-linear Air Quality Index (AQI) formula for 8-hour average ozone concentration, converting a concentration in parts per billion (ppb) into an AQI value on the familiar 0-300+ scale, along with its category (Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, or Very Unhealthy).
This calculator is for general educational reference. For official, real-time air quality readings and health guidance for your area, consult your national or local air quality monitoring agency.