Rex says
Same equations the textbooks use — just way less awkward. Pop in your stats and I'll tell you what the number actually means for you.
Try a scenario
Click to load — tweak from there.Inputs
Result
Cigarette-equivalent exposure
1.14
EPA AQI category (PM2.5)
Unhealthy
24-hr equivalent PM2.5 dose
25.0
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter pm2.5 concentration (µg/m³).
- 2Enter exposure duration (hours).
- 3Read your cigarette-equivalent exposure on the right — it updates as you type.
- 4Hit Share to keep the scenario or send it to someone.
About this calculator
PM2.5 (fine particulate matter under 2.5 microns) is the pollutant most strongly linked to cardiovascular and respiratory harm from both wildfire smoke and everyday air pollution, and its health effects scale roughly with cumulative exposure. Berkeley Earth popularized a rule of thumb — 22 µg/m³ of sustained PM2.5 exposure over 24 hours is roughly equivalent to smoking one cigarette in inhaled particulate burden — as an intuitive translation of an abstract air quality number into something people immediately understand. This calculator applies that ratio, scaled by your actual exposure duration and concentration, and also reports the EPA AQI category so you can see both the intuitive comparison and the official health guidance side by side.
Worked example
Using the values the calculator loads with:
Inputs
- PM2.5 concentration: 75 µg/m³
- Exposure duration: 8 hours
Results
- Cigarette-equivalent exposure: 1.14
- EPA AQI category (PM2.5): Unhealthy
- 24-hr equivalent PM2.5 dose: 25
What each field means
Inputs
- PM2.5 concentration (µg/m³)
- The pm2.5 concentration used in the calculation, measured in µg/m³. Starts at 75 µg/m³ so you have a working example on load. Accepted range: 0–600 µg/m³.
- Exposure duration (hours)
- The exposure duration used in the calculation, measured in hours. Starts at 8 hours so you have a working example on load. Accepted range: 0.5–24 hours.
Results
- Cigarette-equivalent exposure
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- EPA AQI category (PM2.5)
- Returned as a plain value. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- 24-hr equivalent PM2.5 dose
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How reliable is the cigarette-equivalent comparison?
It's a rough intuitive translation, not a precise toxicological equivalence — cigarette smoke and ambient PM2.5 differ in particle composition and co-pollutants. Berkeley Earth's ratio is widely cited by air quality scientists as a useful gut-check, not a clinical dosage measurement.
What PM2.5 levels are common during wildfire smoke events?
Smoke-impacted cities regularly see spikes of 150-300+ µg/m³ during active fire events, occasionally exceeding 500 µg/m³ in the worst hours, compared to a typical 'good' day of under 12 µg/m³ in most US cities.
Should I trust indoor air during a bad outdoor air quality day?
Indoor PM2.5 is usually 30-70% of outdoor levels with windows closed and no filtration, but a HEPA air purifier or a well-sealed HVAC system with a MERV 13+ filter can cut indoor PM2.5 by 80%+ relative to outdoor levels during smoke events.
Why does exposure duration matter as much as concentration?
Cumulative particulate dose is roughly concentration times time, so 8 hours at 75 µg/m³ delivers a similar dose to about 2 hours at 300 µg/m³. Short, intense exposure and long, moderate exposure can be comparably harmful.
Accuracy and limitations
- Population formulas describe averages; individual bodies vary, especially at the extremes of height, age, or muscle mass.
- Results do not account for medical conditions, medication, or pregnancy.
- Use this as a directional reference, not a diagnosis — talk to a clinician before acting on it.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Air Quality Exposure Equivalent Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/air-quality-exposure-equivalent
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/air-quality-exposure-equivalent" target="_blank" rel="noopener">Air Quality Exposure Equivalent Calculator — RevenueLab</a> (2026).</p>
Source: [Air Quality Exposure Equivalent Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/air-quality-exposure-equivalent) (2026).