Air Quality Calculator: AQI Check and Health Guidance

Use the Air Quality Calculator (AQI)

Enter PM2.5, PM10 and ozone to compute AQI with color‑coded categories and guidance. This AQI calculator helps plan activity and ventilation on poor‑air days.

How to Use Air Quality Calculator: AQI Check and Health Guidance

1. Step 1: Enter pollutant values

   Add PM2.5 and PM10 in µg/m³ and ozone in ppb or ppm.

2. Step 2: Set ozone details

   Choose the ozone unit and averaging period (8‑hour or 1‑hour).

3. Step 3: View AQI by pollutant

   See individual AQIs for PM2.5, PM10, and O₃ with color bands.

4. Step 4: Check overall AQI

   The highest pollutant AQI becomes the overall AQI with the dominant pollutant label.

5. Step 5: Follow guidance

   Use the activity and mask/ventilation tips matched to your AQI category.

Key Features

• AQI calculation (PM2.5, PM10, O₃)
• Health impact tier analysis
• Activity recommendations based on AQI
• Mask and ventilation tips

Understanding Results

Formula

We use the standard AQI equation for each pollutant: I = (I_hi − I_lo)/(C_hi − C_lo) × (C − C_lo) + I_lo, where C is your measured concentration, and (C_lo, C_hi) and (I_lo, I_hi) are the breakpoints spanning your value. We round to the nearest whole number for display.

Reference Ranges & Interpretation

Categories are: Good (0–50), Moderate (51–100), Unhealthy for Sensitive Groups (101–150), Unhealthy (151–200), Very Unhealthy (201–300), and Hazardous (301–500). Your overall AQI is the maximum of the pollutant AQIs; that pollutant is the “dominant pollutant.” Use the category to guide activity, ventilation, and masking decisions.

Assumptions & Limitations

Consumer sensors can vary with humidity and placement; different apps may average over different periods. AQI guidance addresses short‑term exposure and is not a medical diagnosis. Use clinical care for personal concerns and follow local public health advisories during severe episodes.

Complete Guide: Air Quality Calculator: AQI Check and Health Guidance

Calculate AQI from PM2.5, PM10, and O₃ with our air quality calculator. Get color‑coded categories, activity guidance, and smart tips for masks and ventilation.

This air quality calculator is designed to be fast, clear, and practical. Enter your PM2.5, PM10, and ozone values, and the tool computes pollutant‑specific AQIs and the overall AQI with a dominant pollutant label. You also get concise activity guidance tailored to the current category, so you can decide whether to open windows, head outside, or grab a respirator.

What is the Air Quality Index (AQI)?

The Air Quality Index translates raw pollution measurements into a single, easy‑to‑read scale from 0 to 500. The higher the AQI, the higher the risk of health effects from short‑term exposure. The scale is divided into six color‑coded categories—Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, and Hazardous—each with plain‑language health messages and activity recommendations.

AQI is intentionally simple so people can make quick decisions without parsing parts‑per‑million or micrograms per cubic meter. Rather than memorizing limits for each pollutant, you only need to know the category you are in and what that means for your plans. The categories also help communities coordinate responses, such as moving school recess indoors or adjusting outdoor work schedules during significant smoke episodes.

AQI values are calculated for individual pollutants using government‑published breakpoints and a linear interpolation formula. In this air quality calculator, we focus on three common pollutants that drive daily AQI in many regions: fine particles (PM2.5), coarse particles (PM10), and ozone (O₃). Your overall AQI is the highest of the pollutant‑specific AQIs, and that pollutant is called the dominant pollutant.

How this air quality calculator works

We implement the standard AQI equation used by U.S. agencies: interpolate the AQI within the range of the breakpoints that contain your measured concentration. For PM2.5 and PM10 we use the 24‑hour breakpoints. For ozone we let you choose the averaging period (8‑hour by default; 1‑hour for high short‑term spikes), because ozone categories above 100 often reference the 1‑hour table. The calculator computes a separate AQI for each pollutant and highlights the maximum as your overall AQI.

Inputs are mobile‑friendly and accept decimals with the phone’s numeric keypad. For ozone you can enter either ppb or ppm; the tool converts ppb to ppm automatically. The result panel shows color‑coded categories, a simple progress bar from 0 to 500, and practical advice like when to limit strenuous outdoor activity or use a well‑fitting respirator.

If you are using a consumer air sensor, remember these devices may be influenced by humidity, particle composition, and placement in your home. When possible, compare your readings with a nearby reference‑grade monitor to calibrate expectations. Even if your absolute values differ from reference monitors, trends (going up or down) are very useful for deciding when to ventilate or when to run an air purifier.

AQI breakpoints and categories

AQI is defined by pollutant‑specific breakpoints—concentration ranges that map to AQI bands. Within a band, linear interpolation yields the exact AQI. For example, if PM2.5 is 35.4 µg/m³, you are at the top of the Moderate category (AQI 100). If PM2.5 rises to 55.5 µg/m³, you cross into Unhealthy for Sensitive Groups (AQI ≥101). The same logic applies to PM10 and ozone using their respective tables.

Categories and health messages are intended for short‑term exposure decisions. Long‑term exposure risk depends on chronic averages and personal factors. Treat the AQI as a helpful, conservative guide for daily planning rather than a medical diagnosis.

AQI values are truncated to integers for communication, but real‑world exposure is continuous. Two days that both report AQI 101 can still feel different depending on how long you are outside, what you are doing, and whether the dominant pollutant is particles or ozone. The most important practice is to pair the category with your own plans: heavy outdoor exertion in orange conditions feels different than a short, casual walk.

PM2.5 vs PM10 vs O₃ explained

PM2.5 refers to airborne particles with diameters ≤2.5 micrometers—tiny enough to travel deep into the lungs. Common sources include wildfire smoke, vehicle exhaust, and indoor combustion. Because of their size, PM2.5 particles are associated with respiratory and cardiovascular effects during elevated episodes, especially for sensitive groups.

PM10 includes larger coarse particles up to 10 micrometers, such as dust and pollen. These particles tend to irritate the upper respiratory tract and the eyes. Episodes of high PM10 often occur with windblown dust or construction.

Ozone (O₃) at ground level forms when sunlight drives reactions of nitrogen oxides and volatile organic compounds. Ozone peaks on sunny afternoons and can cause chest tightness and coughing for some people, particularly during exercise. Unlike particulate matter, ozone is a gas, so filtration requires different strategies than PM.

No single pollutant explains every unpleasant air day. In wildfire season, PM2.5 is often the driver, while in hot, sunny regions during summer, ozone can dominate even when particles are low. Dust events and construction may push PM10 higher than PM2.5. By looking at all three pollutants together, the air quality calculator helps you identify the most relevant action for the day.

Units and averaging periods

Particles (PM2.5 and PM10) are measured in µg/m³ and usually averaged over 24 hours for AQI. Ozone is measured in parts per million (ppm) or parts per billion (ppb). Daily AQI reports often use the 8‑hour ozone average up to AQI 200; higher categories may use 1‑hour ozone thresholds. Our calculator supports both 8‑hour and 1‑hour ozone when you need to assess a short spike.

If your device logs ppb for ozone, enter that and choose “ppb” from the Unit list—the tool converts to ppm for the calculation. For particles, enter your 24‑hour average where possible. If you only have a short‑term reading (for example, a 1‑hour PM spike from cooking), consider that the 24‑hour average may be lower as the day progresses.

Averaging periods matter because your lungs experience both concentration and time. A low concentration for many hours can add up, while a high short‑term spike may have a noticeable immediate effect but contribute less to the daily average. When in doubt, look at both snapshots and averages and choose the more conservative guidance for your activities.

Health advice by AQI category

The color label under your overall AQI summarizes the recommended actions. As a simple rule of thumb: the higher the AQI, the more you should limit intense outdoor activity and the more you should improve your indoor air. For example, many people choose to move workouts indoors once the AQI enters orange (Unhealthy for Sensitive Groups), and most choose to stay indoors with filtered air when AQI is red (Unhealthy) or worse.

• Good (0–50): Enjoy normal outdoor activities.
• Moderate (51–100): Unusually sensitive individuals consider reducing prolonged or heavy exertion.
• USG (101–150): Sensitive groups reduce or reschedule strenuous activity; others monitor symptoms.
• Unhealthy (151–200): Everyone reduce prolonged or heavy exertion outdoors; sensitive groups avoid it.
• Very Unhealthy (201–300): Move activities indoors with clean air; limit time outside.
• Hazardous (301–500): Stay indoors with clean air; follow local public health guidance.

For heat and air quality together, consider also checking the Heat Index Calculator and the UV Index Calculator when the sun is intense. If you want to estimate cumulative risk from time spent in pollution, see our Pollution Exposure Calculator.

Notice how recommendations are phrased as ranges, not absolute rules. Your personal experience matters. Some people feel effects earlier and choose to act more cautiously. Others may tolerate Moderate days without issue. Use the category and your own signals—like coughing during runs or irritated eyes—to guide decisions day by day.

Masks, ventilation and filtration

For particle pollution (PM2.5/PM10), a well‑fitting respirator like an N95 or KN95 can substantially reduce personal exposure, particularly during wildfire smoke events. Indoors, use a HEPA purifier sized for your room and keep windows closed when the outdoor AQI is high. If your HVAC system allows it, upgrade to a higher‑efficiency filter and set the fan to recirculate.

For ozone, filtration is different: standard particulate filters do not remove ozone. Focus on avoiding peak ozone hours (typically afternoon), limiting strenuous outdoor activity, and ventilating with cleaner outdoor air when ozone levels drop. Always balance ventilation with current AQI: when ozone or PM levels are high, prioritize indoor air cleaning over outside air intake.

If you track your well‑being during poor air days, the Oxygen Saturation Calculator and the Respiratory Rate Calculator may be helpful references alongside AQI readings.

A portable CO₂ monitor can complement AQI by telling you when indoor air is becoming stale from humans breathing and poor ventilation. CO₂ is not a pollutant used in AQI, but persistently high indoor CO₂ can indicate that it is time to bring in fresh air—ideally when the outdoor AQI is cleaner. Think of filtration and ventilation as dials you turn up or down depending on both indoor needs and outdoor conditions.

Outdoor exercise and school policies

Outdoor training is more demanding on the lungs, which increases uptake of pollutants when AQI is elevated. Consider rescheduling hard workouts to cleaner times of day, moving them indoors with filtered air, or swapping intensity for lower‑effort activities. Schools and teams often have AQI thresholds for canceling or modifying outdoor practices; check local guidance and adapt based on participants’ sensitivity.

Hydration and recovery matter too. On hot, smoky days, it’s easy to under‑hydrate, especially when exercising indoors. Use our Hydration Calculator to plan fluid intake if you’re training during a pollution episode.

If you are responsible for group activities, prepare a simple playbook: identify AQI cutoffs for cancellations, communicate mask and indoor space options, and keep parents and participants informed about the day’s plans. The consistency of this approach removes guesswork when conditions change quickly.

Tips for sensitive groups

Sensitive groups include people with asthma or other lung conditions, older adults, children and teens, pregnant people, and those with cardiovascular disease. If you fall into one of these groups, consider acting one category “earlier” than the general population. For instance, you might begin limiting outdoor exertion once AQI moves from Moderate to USG (orange), especially if you notice symptoms like coughing or chest tightness.

Build a simple home plan: a small room with a HEPA purifier for smoky days, a couple of well‑fitting respirators on hand, and a personal threshold for moving exercise indoors. Keep your medications accessible and follow your clinician’s action plan if you have one.

For kids and teens, consider indoor alternatives that keep them active without exposure—short circuits, skill drills, or games in a well‑filtered gym room. For older adults, plan errands for the cleanest times of day and choose routes away from heavy traffic when possible. If you are pregnant, discuss air quality strategies during prenatal visits and aim for consistent clean‑air routines at home.

Frequently asked clarifications

Why does my overall AQI differ from my sensor app? Different apps may average over different time windows or use slightly different breakpoints or rounding. Our calculator follows a straightforward breakpoint interpolation and shows the maximum of pollutant AQIs as your overall AQI.

Why offer both 8‑hour and 1‑hour ozone? Daily AQI is often reported with 8‑hour ozone for AQI ≤200. For higher ozone events, health messaging sometimes uses 1‑hour breakpoints; the toggle helps when you need to gauge a short‑term spike.

How do I improve indoor air quickly? Run a properly sized HEPA purifier on high, close windows when outdoor air is worse, and reduce indoor sources (smoking, candles, high‑heat cooking). A DIY box‑fan filter can be a temporary stopgap for small spaces.

Sources: See U.S. EPA materials on AQI breakpoints and health messaging.
AirNow: AQI Basics

Frequently Asked Questions