20x25x4 MERV 13 Furnace & AC Air Filter
The 20x25x4 (actual size 19.5 × 24.5 × 3.75 in) in MERV 13 — captures everything MERV 11 does plus smoke, bacteria and virus-carrying particles. Best for allergy and asthma sufferers, and homes dealing with wildfire smoke. 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 20x25x4x4 slot — step up for finer filtration, down for easier airflow.
Measured your slot? Other depths
Depth must match your filter slot exactly. Same 20x25x4 face, different thickness.
Frequently asked questions
What is the actual size of a 20x25x4 air filter?
A 20x25x4 is the nominal size printed on the frame. The true measured size is about 19.5 × 24.5 × 3.75 in, cut slightly under so the filter slides into the 20x25 slot. This is standard across all brands.
What does MERV 13 filter out?
MERV 13 captures everything MERV 11 does plus smoke, bacteria and virus-carrying particles. It's best for allergy and asthma sufferers, and homes dealing with wildfire smoke. On the box you may see it labelled MPR ~1500–1900 (3M/Filtrete) or FPR 10 (Home Depot).
How often should I change a 20x25x4x4 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 20x25x4x4 filter fit my furnace?
Air filters are universal by size — any furnace, AC or return grille that takes a 20x25x4x4 filter will fit this one, regardless of the HVAC brand. Just match the three numbers on your old filter's frame exactly, depth included.