DIY air cleaner calculator
DIY Air Cleaner & Corsi–Rosenthal Box Calculator
Choose an EPA-tested 20-inch box-fan configuration using 20×20-inch MERV 13 filters, then estimate CADR, air changes per hour, five-ACH coverage, cleaner count and material cost.
Size a DIY air cleaner for your room
Select one of the EPA-tested 20-inch box-fan configurations with 20×20-inch MERV 13 filters. The CADR values are experimental estimates for those specific builds, not guaranteed output from every fan, filter or finished device.
Estimated DIY clean-air plan
Single 20×20×1-inch MERV 13 filter with shroud: approximately 156 ± 4 CFM per unit in the referenced EPA experiment.
Estimated total CADR
156 CFM
Achieved air changes/hour
6.5 ACH
Recommended cleaner count
1 at 5 ACH
Selected setup coverage at 5 ACH
234 ft²
Required CADR
120 CFM
Room volume
1440 ft³
Five-ACH planning check
The selected 1-cleaner setup reaches the 5 ACH planning target in this idealized model.
Material-cost estimate
Add a material cost per cleaner to compare the selected setup with the recommended count.
Build and fire-safety checklist
- Use a 2012-or-newer box fan verified to UL 507 or an equivalent standard, such as a fan carrying a UL or ETL safety mark.
- Follow the fan manufacturer’s instructions, never use an extension cord, and do not use a damaged cord, plug or fan.
- Do not leave children unattended while the fan is running, and make sure working smoke detectors are installed throughout the home.
- Keep the intake and outlet clear, place the build where it cannot tip, and confirm airflow follows the filter arrows.
- Replace filters when they look dirty or begin to release smoke odors, and replace any filter that is wet or damaged.
- Do not treat this estimate as a substitute for local smoke alerts, source control, ventilation guidance or a commercially certified air cleaner.
Estimates assume a well-mixed room, no continuing particle source, no extra leakage, clean filters and additive clean-air delivery from identical units. Actual CADR and room performance can be lower.
How the DIY air cleaner estimate works
- The five presets reproduce EPA experiments with a 20-inch box fan and 20×20-inch MERV 13 filters: 111 ± 1, 156 ± 4, 248 ± 15, 263 ± 22 and 401 ± 31 CFM for the listed basic, shrouded and Corsi–Rosenthal configurations.
- Achieved air changes per hour equals the selected cleaners’ estimated total CADR multiplied by 60, divided by room volume in cubic feet.
- Recommended count and floor-area coverage use a transparent five-ACH planning target and the ceiling height you enter.
- Material cost is your per-cleaner amount multiplied by count. It excludes electricity, labor, tools, replacement filters and taxes.
Air quality tools for the decision in front of you
Start with the number or question you already have. Every tool leads to a concrete calculation, comparison, or action plan instead of another generic article.
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Air purifier electricity cost calculator
Calculate electricity, filter, annual, and three-year costs for one or more air purifiers.
Daily air pollution exposure planner
Combine the places in your day into a time-weighted PM2.5 comparison.
Trust Signals
Use experimental CADR as a planning estimate
Review policy
August 8, 2026. We update supporting pages when calculator logic, live data behavior, or source framing changes.
Primary sources
AQI uses EPA / AirNow breakpoint logic. Cigarette-equivalent framing follows Berkeley Earth’s PM2.5 interpretation.
Live data layer
City pages use EPA AirNow where supported, with cached fallbacks and planning baselines if the API fails or coverage is unavailable.
DIY air cleaner calculator questions
Are these CADR values guaranteed for my build?
No. They are EPA experimental measurements for specific tested fans, filters, shrouds and assemblies. Fan model, filter resistance, seals, placement, filter loading and construction quality can change real output.
Why does the calculator use five air changes per hour?
Five ACH is a practical planning target used here to compare configurations consistently. It is not a universal safety threshold, and actual smoke control also depends on leakage and continuing outdoor or indoor particle sources.
Can I add CADR from multiple DIY cleaners?
For an idealized room-planning estimate, the calculator adds the same tested CADR for each identical unit. Real combined performance can be lower if airflow is obstructed, units interfere or filters load unevenly.
Does the cost estimate include electricity and new filters?
No. It only multiplies the optional material cost you enter by the selected or recommended cleaner count. Operating energy, tools, labor, tax and future filter replacements are excluded.