Start here: the recommended sequence
Use these free tools in sequence to avoid repeating work: measure the room and get a CADR target, check air changes per hour (ACH), estimate running and filter costs, set a filter-replacement schedule, then compare shortlisted units or run the quick finder. The tools are practical, free, and aimed at homeowners, renters and small offices; you can jump straight to any tool if needed.
Tools grouped by task
Measure & size
- Air Purifier Size & CADR Calculator — Enter room dimensions or area to get a recommended CADR and unit size. Use when you know the room and need a performance target.
Performance checks
- Air Changes Per Hour (ACH) Calculator — Convert CADR or airflow into ACH to check whether a particular device meets your air-change goals (useful for allergies, smoke or high-occupancy rooms).
Costs & maintenance
- Air Purifier Running Cost Calculator — Estimate electricity and filter expenses over months or years to compare total ownership cost.
- Air Purifier Filter Replacement Reminder — Create a simple replacement schedule and reminders based on your expected daily runtime and filter life.
Choose & compare
- Compare Air Purifiers Side by Side — Place 2–4 shortlisted models next to each other for a clear spec and feature comparison.
- Find Your Air Purifier in 60 Seconds — A quick guided selector that returns a short shortlist from room, budget and key-feature inputs.
Compare your shortlist once you have CADR and cost estimates — the comparison tool helps turn targets into a final choice without hard selling.
Decision flow and practical tips
Run the calculators in the order above to keep inputs consistent: take a single set of room measurements and reuse them across the Size, ACH and Cost tools. Start with the Size & CADR Calculator to define a performance target; use that CADR in the ACH Calculator to see the resulting air changes per hour and decide if you need a higher target for your situation.
When interpreting results, remember three common trade-offs: higher fan speeds raise CADR but increase noise; higher CADR often means higher energy use; and larger or more powerful purifiers typically cost more to buy and to maintain. The Running Cost Calculator asks for wattage and filter prices — if a spec is missing on a product page, use the manufacturer’s published wattage or a reasonable estimate to compare models fairly.
For open-plan or irregular spaces, size each distinct area separately and prioritize the space where people spend the most time (sleeping areas, home offices). If a single purifier must serve connected rooms, choose the highest CADR suggested or combine two smaller units rather than relying on one undersized device.
Use the Filter Replacement Reminder after you select a model: enter your expected daily runtime and the filter life listed by the manufacturer to generate calendar reminders. This keeps performance near the level your initial sizing assumed and avoids surprises from reduced airflow or clogged filters.
If you want a quick route to a shortlist, run the 60-second Finder and then validate the top picks with the Size, ACH and Running Cost calculators before deciding.
Most asked
Q: Which tool sizes a room? — A: The Air Purifier Size & CADR Calculator generates recommended CADR and unit size from your room dimensions.
