SmogRank / Scales

One reading, every scale

Monitors measure fine particles in µg/m³. Each country turns that number into its own index, with its own bands and cut-offs, so the same air can be Moderate in one place and Poor in the next. Put in a reading to see it on all 7 scales we show, or start from an index number.

Try 15.0 µg/m³ (the WHO's 24-hour guideline) or 102.4 µg/m³ (Singapore over the last 24 hours).

µg/m³101.2 µg/m³Unhealthy

US AQI Your scale183Unhealthy

India AQI235Poor

China AQI133Lightly polluted

European AQI101 µg/m³Very poor

UK DAQI10Very high

Canada AQHI+10+Very high risk

Bands on one µg/m³ axis, stretched near zero (square root) so the clean end has room; the dashed line is the WHO's 24-hour guideline, 15 µg/m³.

The scales

µg/m³: what the monitors measure, coloured here by the US EPA's PM2.5 categories.
US AQI: the US Environmental Protection Agency (EPA). The official index in the United States, shown on AirNow and by many weather and air apps worldwide; its PM2.5 cut-offs were lowered in February 2024.
India AQI: India's Central Pollution Control Board (CPCB). India's National Air Quality Index, on CPCB's daily bulletins and the state boards' dashboards.
China AQI: China's Ministry of Ecology and Environment (standard HJ 633-2012). China's official index, reported by the national monitoring centre and every city's environment bureau.
European AQI: the European Environment Agency (EEA). The European Air Quality Index, for the EEA's member and cooperating countries; it gives bands, not a number, and its cut-offs were lowered in 2024.
UK DAQI: the UK's Department for Environment, Food and Rural Affairs (Defra). The UK's Daily Air Quality Index, on UK-AIR's forecasts and alerts across the four nations.
Canada AQHI+: Environment and Climate Change Canada with Health Canada. Canada's Air Quality Health Index, read here from PM2.5 alone (AQHI+), which is how it answers wildfire smoke within the hour.

Each scale here is its PM2.5 part only. Official indexes take the worst of several pollutants, so a city's official number can be higher. The scales are defined on 24-hour means (AQHI+ on hourly ones); how we use them.

Nothing on SmogRank is medical advice. For health guidance during bad air, follow your local health authority.