Environment
Air Quality Index (AQI) Calculator
Convert pollutant concentration into AQI, estimate overall AQI from multiple pollutants, and understand what each AQI category means for exposure and health.
AQI Calculator & Category Interpreter
Calculate AQI sub-index by pollutant, compute overall AQI across pollutants, and get clear category guidance.
| AQI Range | Category | PM2.5 (µg/m³) | PM10 (µg/m³) | O₃ 8-hour (ppm) | CO 8-hour (ppm) | NO₂ 1-hour (ppb) | SO₂ 1-hour (ppb) |
|---|---|---|---|---|---|---|---|
| 0–50 | Good | 0.0–9.0 | 0–54 | 0.000–0.054 | 0.0–4.4 | 0–53 | 0–35 |
| 51–100 | Moderate | 9.1–35.4 | 55–154 | 0.055–0.070 | 4.5–9.4 | 54–100 | 36–75 |
| 101–150 | Unhealthy for Sensitive Groups | 35.5–55.4 | 155–254 | 0.071–0.085 | 9.5–12.4 | 101–360 | 76–185 |
| 151–200 | Unhealthy | 55.5–125.4 | 255–354 | 0.086–0.105 | 12.5–15.4 | 361–649 | 186–304 |
| 201–300 | Very Unhealthy | 125.5–225.4 | 355–424 | 0.106–0.200 | 15.5–30.4 | 650–1249 | SO₂ uses 24-hour ≥200 |
| 301–500 | Hazardous | 225.5–325.4 | 425–604 | O₃ uses 1-hour ≥301 | 30.5–50.4 | 1250–2049 | SO₂ 24-hour: 605–1004 |
AQI is computed by converting each pollutant to a sub-index using breakpoint interpolation, then taking the maximum sub-index as the overall AQI. Some pollutants use special rules at very high levels (for example, ozone and SO₂).