Type your size (like 20x25x1) or use the dropdowns. We only show sizes we actually carry — no dead ends.
Length and width are interchangeable — we’ll find it either way.
Not sure of your size? It takes 30 seconds.
Air filter sizes read as Length × Width × Depth, in inches.
Pull your current filter
Slide out the filter in your return vent or air handler. Power the system off first.
Check the printed size
Most filters have the size stamped on the cardboard frame, like 20x25x1. That’s the number you order by.
No print? Measure & round up
Measure all three sides with a tape and round each up to the nearest inch. That’s your nominal size.
⚠ The one thing that trips people up: nominal vs. actual size
The size printed on the frame (the nominal size) is rounded up. The filter itself measures about ½ inch smaller per side — a 20x25x1 filter actually measures about 19.5 x 24.5 x 0.75. That gap is normal and lets the filter seat properly. Always order by the nominal (printed) size. Managing dozens of mixed sizes across a property? That’s exactly what our free site audit is for — we map every one so you never guess again.