18x24x1 MERV 11 Furnace & AC Air Filter
The 18x24x1 (actual size 17.5 × 23.5 × 0.75 in) in MERV 11 — captures everything MERV 8 does plus pet dander, fine dust and smog particles. Best for homes with pets or mild allergies. Below: the true dimensions, when to change it, and how this MERV compares to the others that fit the same slot.
Same size, other MERV ratings
All fit your 18x24x1x1 slot — step up for finer filtration, down for easier airflow.
Measured your slot? Other depths
Depth must match your filter slot exactly. Same 18x24x1 face, different thickness.
Frequently asked questions
What is the actual size of a 18x24x1 air filter?
A 18x24x1 is the nominal size printed on the frame. The true measured size is about 17.5 × 23.5 × 0.75 in, cut slightly under so the filter slides into the 18x24 slot. This is standard across all brands.
What does MERV 11 filter out?
MERV 11 captures everything MERV 8 does plus pet dander, fine dust and smog particles. It's best for homes with pets or mild allergies. On the box you may see it labelled MPR ~1000–1200 (3M/Filtrete) or FPR 7 (Home Depot).
How often should I change a 18x24x1x1 filter?
Change it every 60–90 days. A 1" filter clogs quickest, so check it monthly. A clogged filter strains your blower and raises energy bills.
Will a 18x24x1x1 filter fit my furnace?
Air filters are universal by size — any furnace, AC or return grille that takes a 18x24x1x1 filter will fit this one, regardless of the HVAC brand. Just match the three numbers on your old filter's frame exactly, depth included.