HEPA Filter Replacement Calculator
Air purifier manuals list filter life as a single number, usually between six and twelve months, which ignores the reality that a filter running four hours a day lasts dramatically longer than one running nonstop in a smoker or pet heavy home. This calculator takes your honest daily run hours and a rough indoor air quality rating, then projects when the filter will hit the end of its useful life. The underlying math assumes a filter rated for 4,000 hours of use at typical loading, with multipliers for air quality conditions like heavy cooking smoke, pet dander, or wildfire events. Use the output to set a calendar reminder rather than waiting for the purifier indicator, which often triggers based on time rather than actual saturation. Check the pre filter monthly regardless of this schedule.
Three tips before you buy
- Stock one spare filter at purchase. The brand specific replacements often go out of stock for weeks at a time.
- Label the install date on the filter edge with a marker. Memory fails, receipts get lost.
- Third party filters can be cheaper but confirm they match the original H13 or H14 rating before buying.
FAQ
Can I wash a HEPA filter?
No. Washing damages the fiber structure and voids certified HEPA performance. Vacuum the pre filter instead and replace the HEPA stage on schedule.
Does smoke shorten filter life?
Yes. Wildfire smoke or heavy cooking can halve the life of an activated carbon pre filter and shorten the HEPA stage by about a third.
How do I know a filter is spent?
Airflow drops noticeably and smells stop getting cleared in the same time. Some purifiers include a filter life indicator that flashes when replacement is due.