14x18x4 MERV 11 Furnace & AC Air Filter
The 14x18x4 (actual size 13.5 × 17.5 × 3.75 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 14x18x4x4 slot — step up for finer filtration, down for easier airflow.
Measured your slot? Other depths
Depth must match your filter slot exactly. Same 14x18x4 face, different thickness.
Frequently asked questions
What is the actual size of a 14x18x4 air filter?
A 14x18x4 is the nominal size printed on the frame. The true measured size is about 13.5 × 17.5 × 3.75 in, cut slightly under so the filter slides into the 14x18 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 14x18x4x4 filter?
Change it every 6–12 months. A 4" filter holds more dust and lasts longer, but still check it periodically. A clogged filter strains your blower and raises energy bills.
Will a 14x18x4x4 filter fit my furnace?
Air filters are universal by size — any furnace, AC or return grille that takes a 14x18x4x4 filter will fit this one, regardless of the HVAC brand. Just match the three numbers on your old filter's frame exactly, depth included.