The timing, plainly
How often should you change the furnace filter?
For standard 1-inch filters, every 1–3 months — closer to monthly during heavy heating or cooling season, with pets, or with allergies in the house. Thick media filters (4–5 inch) typically run 6–12 months. Nobody fails at knowing this; everyone fails at remembering it in month three.
Airflow drops as the filter loads up — the system runs longer, costs more, and wears faster. The recurring reminder is the whole solution.
Where it sits in the year
Ordered from this month — this is the shape of it on a timeline.
Which direction does the filter arrow point?
The arrow points in the direction of airflow — toward the furnace/blower, away from the return duct. Writing the install date on the frame when you change it makes the next reminder self-verifying.
Do expensive filters last longer?
Higher MERV ratings filter finer particles but can load up faster and restrict airflow more, not less. Thickness is what buys time: 4–5 inch media filters run 6–12 months where 1-inch filters run 1–3.
The date is the easy part. Remembering is the product.
Reviewal keeps windows like this on one page — the whole year of them — and emails you before each one opens. Your calendar handles what's today; this is the layer above it. Free to start: 40 events, 3 sections, reminders included.
Tracking this in a spreadsheet or calendar today? See exactly what changes: vs. a spreadsheet · vs. calendar reminders