Updated
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).