AQI Calculator (PM2.5 + PM10)
Use measured particulate concentrations to estimate the U.S. AQI (Air Quality Index). Enter one or both values below.
This tool is for educational use and uses EPA breakpoint interpolation. For health-critical decisions, follow local official AQI reporting.
What this air quality calculator does
This air quality calculator converts particulate matter measurements into an estimated AQI score so you can quickly understand risk level and make practical choices. AQI turns raw concentration data into a scale from 0 to 500. The higher the number, the higher the potential health concern.
The calculator supports two common particulate metrics:
- PM2.5 (fine particulate matter): tiny particles that can penetrate deep into the lungs.
- PM10 (coarse particulate matter): larger particles that can irritate airways and worsen respiratory symptoms.
If you provide both values, the tool computes each sub-index and reports the highest one as the final AQI, which matches how AQI is typically interpreted in public reporting.
Why AQI matters for everyday decisions
You do not need to be an atmospheric scientist to benefit from AQI. A single number can guide simple daily choices: whether to jog outside, open windows, use air purification, or limit strenuous activity. AQI is especially useful during wildfire smoke events, temperature inversions, or high-traffic days.
Sensitive groups may be affected earlier than healthy adults. That includes children, older adults, pregnant individuals, and people with asthma, COPD, or cardiovascular disease. For these groups, moving from “Moderate” to “Unhealthy for Sensitive Groups” can be a meaningful shift.
How the AQI calculation works
1) Find the concentration interval
For each pollutant, AQI uses defined concentration breakpoints. The measured concentration is matched to the interval where it belongs.
2) Interpolate inside that interval
A linear interpolation formula maps your concentration to an AQI value inside the associated AQI band. This gives a smoother and more informative result than simply assigning the entire band.
3) Take the highest pollutant sub-index
When multiple pollutant values are available, the highest sub-index determines the final AQI category because it represents the dominant short-term risk driver.
| AQI Range | Category | General Guidance |
|---|---|---|
| 0–50 | Good | Air quality is satisfactory for most people. |
| 51–100 | Moderate | Usually acceptable; unusually sensitive people should monitor symptoms. |
| 101–150 | Unhealthy for Sensitive Groups | At-risk populations should reduce prolonged outdoor exertion. |
| 151–200 | Unhealthy | Everyone may begin to feel effects; sensitive groups face higher risk. |
| 201–300 | Very Unhealthy | Health alert conditions; avoid outdoor exertion when possible. |
| 301–500 | Hazardous | Emergency conditions; minimize outdoor exposure and use filtration. |
PM2.5 vs PM10: what is the practical difference?
PM2.5 is often more strongly linked to serious cardiopulmonary outcomes because of its small size and ability to reach deep lung tissue. PM10 can still be harmful, especially for people with allergies, asthma, or airway inflammation, and can spike during dust or wind events.
- Wildfire smoke: usually drives PM2.5 sharply upward.
- Construction and road dust: often elevates PM10.
- Urban traffic: can contribute to both, especially near busy roads.
How to lower exposure when AQI is high
At home
- Run a HEPA air purifier sized for your room.
- Keep windows and doors closed during high-smoke or dust periods.
- Use HVAC filters rated MERV 13 or better if your system supports them.
- Avoid indoor particle sources (candles, frying, smoking) during poor-air days.
Outdoors
- Reduce vigorous exercise when AQI is above 100.
- Choose lower-traffic routes for walking and biking.
- Use a well-fitted respirator (such as N95) in smoke-heavy conditions.
- Schedule outdoor tasks earlier or later based on hourly AQI trends.
Interpreting your result responsibly
This calculator gives a solid estimate, but local official AQI can differ due to averaging windows, monitor calibration, and nearby micro-environments. Treat your result as a fast decision aid, not as a replacement for public health alerts.
If someone in your household has respiratory or cardiac symptoms, use a conservative approach even at moderate AQI. Symptoms can vary by person, and personal thresholds may be lower than population-level guidance.
Frequently asked questions
Is AQI the same everywhere in the city?
No. Air quality can vary significantly block by block due to roads, industry, terrain, and weather patterns.
Can indoor AQI be better than outdoor AQI?
Yes, especially with filtration and controlled ventilation. But indoor sources can also worsen air if unmanaged.
Should I rely only on PM measurements?
PM2.5 and PM10 are important, but ozone, NO2, and other pollutants also matter. Use local environmental agency data for a complete view.
Bottom line
A practical air quality calculator helps turn raw sensor numbers into action. Use it to decide when to exercise outside, when to filter indoor air, and when to reduce exposure. Small daily choices based on AQI can add up to meaningful long-term health protection.