Furnace Filter Size Guide — Find Your Filter in Under 2 Minutes
Furnace Filter Size Guide — Find Your Filter in Under 2 Minutes
Step 1 — Find your existing filter
Located inside your furnace or in a return air duct grille on your wall or ceiling.
Step 2 — Read the size from the filter frame
Every filter has its size printed on the frame — three numbers like 16x25x5 (width × height × depth in inches).
Step 3 — Understand nominal vs actual size
The nominal size is slightly larger than the actual physical size. Always order by the nominal size — never measure the slot.