Size directory
Furnace filter sizes: find your exact replacement
The number on the cardboard frame is the size you order. It is a rounded label, not the tape-measure reading. Pick the printed size below, then check the actual dimensions on the size page before you buy.
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Size finder
No size on this list matches that. Try the printed whole-inch number, or measure the old filter.
Those “typical actual” figures are a shorthand. Brands cut the same label size differently — see each size page. More sizes will be added; all listed sizes.
How to read the number on the filter
The frame is printed with three numbers, almost always in inches, in this order:
- Width — one face dimension (example: 16).
- Length — the other face dimension (example: 25).
- Thickness — how deep the slot is (example: 1, 2, 4, or 5).
So 16x25x1 means a one-inch-class filter whose shopping size is 16 by 25 inches. Buy that printed size. Do not order the fractional number your tape measure shows, or the replacement will be too small or will not go in.
If the print is faded, pull the filter out, measure length, width, and thickness, and round each face dimension up to the nearest whole inch. A filter that measures about 15.75 by 24.75 by 0.75 is a 16x25x1.
Width and length can swap on the label (25x16x1 is the same size as 16x25x1). We list the conventional smaller-or-standard × longer × thickness form.
Measure before you reorder
Nominal vs. actual is the usual reason a new filter does not fit. A 16x25x1 is usually about 15.75 × 24.75 × 0.75 inches, but Filtrete, Honeywell, Nordic Pure, and Amazon Basics do not cut it identically.