Chapter 01Records · Practical note
Air filter change reminders that actually stick
Set two reminders, not one. A monthly look on a fixed day, because ENERGY STAR says to inspect, clean or change the filter once a month, and a change window 60 to 90 days after the filter went in, the range the EPA says makers typically recommend. Write the date in on the filter frame, name the reminder with the slot and size, and keep the next filter next to the unit. For a filter put in on October 5, 2026, that is checks on November 5, December 5 and January 5 and a change between December 4 and January 3.
Source: ENERGY STAR maintenance checklist, checked October 15, 2026; EPA, Guide to Air Cleaners in the Home, checked October 9, 2026.
- Look at the filter once a monthMonthly ENERGY STAR maintenance checklist, October 15, 2026
- Days to a change, as makers typically recommend60 to 90 EPA, Guide to Air Cleaners in the Home, October 9, 2026
- Filters a year for each slot4 to 6 EPA, Guide to Air Cleaners in the Home, October 9, 2026
Why one reminder isn't enough
There are two numbers to remember, and they do different jobs. ENERGY STAR's maintenance checklist says to inspect, clean or change the filter once a month. The EPA's guide to air cleaners says manufacturers typically recommend a new filter every 60 to 90 days. The monthly look catches a filter that loads early. The change window catches the one that looks fine but has been in too long.
Source: ENERGY STAR maintenance checklist, checked October 15, 2026; EPA, Guide to Air Cleaners in the Home, checked October 9, 2026.
A single "change filter every 3 months" reminder misses both. It is easy to snooze, and it never asks you to look.
Set it up once
Write the date in on the frame
Use a marker on the edge of the new filter before it goes in: IN and the date. Anyone who opens the grille can see how long it has been.
Pick a fixed check day
The same date every month, or the day you do a monthly walk of the house. Make it a repeating reminder.
Name it with the slot and size
Filter check, hall, 20x25x1. Then the reminder also tells you what to buy.
Add the change window
A one-off reminder 60 days after the date in, saying the window is open, and a second at 90 days.
Put the next filter by the unit
When the spare is already there, changing it takes a minute.
Source: EPA, Guide to Air Cleaners in the Home, checked October 9, 2026.
The worked dates
The filter size finder's worked example is a 20x25x1 put in on October 5, 2026. It gives monthly checks on November 5, December 5 and January 5, and a change window from December 4, 2026, at 60 days, to January 3, 2027, at 90 days. A check that finds the filter dirty earlier ends the window early: change it and start again from the new date.
Source: EPA, Guide to Air Cleaners in the Home, checked October 9, 2026; ENERGY STAR maintenance checklist, checked October 15, 2026.
Turn it off before you pull it
Filterbuy's measuring guide says to turn the system off at the thermostat before you pull the filter, and to note the airflow arrow so the new one goes in the same way.
Source: Filterbuy, How to Measure Your Air Filter, checked October 9, 2026.
Anchor it to dates you already keep
ENERGY STAR suggests planning heating and cooling check-ups around the spring and fall time changes. NIST lists those as the second Sunday of March and the first Sunday of November. Those two weekends are good backstops: if the filter's date in is more than 90 days back when the clocks change, change it then.
Source: ENERGY STAR maintenance checklist, checked October 15, 2026; NIST, daylight saving time rules, checked October 12, 2026.
- Monthly: the check day you picked, every slot.
- Every 60 to 90 days: the change window, from the date on the frame.
- Spring and fall time changes: the backstop, and the day to restock spares.
Source: ENERGY STAR maintenance checklist, checked October 15, 2026; EPA, Guide to Air Cleaners in the Home, checked October 9, 2026; NIST, daylight saving time rules, checked October 12, 2026.
Let the tool do the arithmeticHVAC filter size finder and replacement plannerPut in the size on the frame and the date the filter went in. The finder gives the change window and the three monthly check dates to put in your calendar, and prints a filter record to keep by the unit.Example: 19.5 x 24.5 x 0.75 in (Actual size of a 20x25x1 filter)Open the toolKeep the spares coming
At 60 to 90 days a change, one slot uses 4 to 6 filters a year. Buy at least the next one when you put a filter in, and restock on the time change weekends. When you take the last spare off the shelf, that is the reminder to order.
Source: EPA, Guide to Air Cleaners in the Home, checked October 9, 2026.
Checklist to print
Ten minutes, once:
- Date in written on the new filter's frame
- Monthly check day picked, as a repeating reminder
- Reminder named with the slot and the filter size
- Change window reminders at 60 and 90 days from the date in
- Next filter on the shelf by the unit
- Time change weekends on the calendar as the backstop
- Each change written in the filter log
Tips and tricks
- Tip 01
Put the filter on the monthly walk
If you already walk the house once a month to test alarms or read the meter, add the filter look to the same walk instead of a separate reminder.
- Tip 02
Snooze the change, not the check
The monthly look takes a minute. If you snooze anything, snooze the change reminder, and only until the check day.
- Tip 03
Thicker filters: read the package
Filterbuy's chart lists 1, 2 and 4-inch filters as separate sizes. If a thicker filter's package gives its own change interval, use that for the window and keep the monthly look.
Source: Filterbuy air filter size chart, checked October 9, 2026.
- Tip 04
Tell the household
Write the check day on the filter log by the unit so anyone in the house, or a sitter, can do it.
What we would do
A monthly look plus a 60 to 90 day window
Write the date in on the frame, set a repeating monthly reminder named with the slot and size, add reminders at 60 and 90 days, and keep the next filter by the unit. Use the time change weekends as the backstop and to restock.
Source: ENERGY STAR maintenance checklist, checked October 15, 2026; EPA, Guide to Air Cleaners in the Home, checked October 9, 2026.
Questions
How often should I check my air filter?
Once a month, according to ENERGY STAR's checklist: inspect it, and clean or change it if it needs it.
Source: ENERGY STAR maintenance checklist, checked October 15, 2026.
How often should I change my air filter?
The EPA says manufacturers typically recommend a new filter every 60 to 90 days. Change it sooner if the monthly look shows it dirty.
Source: EPA, Guide to Air Cleaners in the Home, checked October 9, 2026.
Should I write the date on my air filter?
It helps. Write IN and the date on the frame edge before it goes in, and anyone who opens the grille can see how long it has been in.
What's a good day to remember to change the filter?
A fixed day each month for the check, plus the spring and fall time changes as a backstop. ENERGY STAR suggests planning check-ups around the time changes.
Source: ENERGY STAR maintenance checklist, checked October 15, 2026.
How many filters should I keep on hand?
At least the next one for each slot. A year at 60 to 90 days per change is 4 to 6 per slot.
Source: EPA, Guide to Air Cleaners in the Home, checked October 9, 2026.
The tool and more guides
Chapter 01HVAC filter size finder and replacement plannerTurn a nominal size like 16x25x1 into the filter's actual dimensions, or measure an old filter to find the size to buy, then plan the next change.Open the tool
ProblemNo size printed on my air filter: how to find itThe print on the frame is gone or the slot is empty. Measure the opening, round to the nearest inch, and know when you need a custom size.Read the guide
Practical noteWhat to change on move-in day: locks, garage opener and codesNew house, old keys. Here's the order to work in on move-in week: count what you got, change the locks, clear the garage opener, reset codes, then cut copies.Read the guide- Chapter 01All records toolsPrintable home records with a calculator behind each one: appliance and warranty log, HVAC filter sizes and change dates.Open the chapter
Sources
- Heating and Cooling Maintenance Checklist, ENERGY STAR (U.S. EPA and DOE). Checked October 15, 2026.
- Guide to Air Cleaners in the Home, U.S. Environmental Protection Agency. Checked October 9, 2026.
- How to Measure Your Air Filter: Complete Step-by-Step Guide, Filterbuy (US air filter manufacturer). Checked October 9, 2026.
- Daylight Saving Time Rules, National Institute of Standards and Technology (NIST). Checked October 12, 2026.
- Air Filter Sizes: Nominal vs. Actual Dimensions, Filterbuy (US air filter manufacturer). Checked October 9, 2026.
Every outside number on this page names its source and the date we checked it. See them all on the sources page. Spotted an error? Tell us.