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.

Size finder

No size on this list matches that. Try the printed whole-inch number, or measure the old filter.

• 20x20x1Typical actual ~19.75×19.75×0.75Full page
• 16x25x1Typical actual ~15.75×24.75×0.75Full page
• 16x20x1Typical actual ~15.75×19.75×0.75Full page
• 20x25x1Typical actual ~19.75×24.75×0.75Full page
• 14x25x1Typical actual ~13.75×24.75×0.75Full page
• 16x24x1Typical actual ~15.75×23.75×0.75Full page
• 14x20x1Typical actual ~13.75×19.75×0.75Full page
• 18x24x1Typical actual ~17.81×23.81×0.81Full page
• 16x30x1Typical actual ~15.81×29.81×0.81Full page
• 20x22x1Typical actual ~19.81×21.81×0.81Full page
• 12x24x1Typical actual ~11.75×23.75×0.75Full page
• 16x25x4Typical actual ~15.94×24.87×4.38Full page
• 20x25x4Typical actual ~19.94×24.88×4.38Full page
• 16x20x4Typical actual ~15.88×19.88×4.38Full page
• 20x20x4Typical actual ~19.94×19.75×4.38Full page
• 16x25x2Typical actual ~15.5×24.5×1.75Full page
• 20x25x2Typical actual ~19.5×24.5×1.75Full page
• 20x20x2Typical actual ~19.5×19.5×1.75Full page
• 16x20x2Typical actual ~15.5×19.5×1.75Full page
• 16x25x5Typical actual ~15.75×24.75×4.38Full page
• 20x25x5Typical actual ~19.88×24.88×4.38Full page
• 16x20x5Typical actual ~15.88×19.75×4.38Full page
• 20x20x5Typical actual ~19.63×19.88×4.38Full page
• 20x30x1Typical actual ~19.5×29.5×0.75Full page
• 14x30x1Typical actual ~13.68×29.68×0.81Full page
• 18x20x1Typical actual ~17.75×19.75×0.75Full page
• 24x24x1Typical actual ~23.68×23.68×0.81Full page
• 20x24x1Typical actual ~19.75×23.75×0.75Full page
• 14x24x1Typical actual ~13.75×23.75×0.75Full page
• 14x14x1Typical actual ~13.75×13.75×0.75Full page
• 12x12x1Typical actual ~11.75×11.75×0.75Full page
• 16x16x1Typical actual ~15.81×15.81×0.81Full page
• 18x18x1Typical actual ~17.81×17.81×0.81Full page
• 25x25x1Typical actual ~24.81×24.81×0.81Full page
• 12x20x1Typical actual ~11.75×19.75×0.75Full page
• 20x23x1Typical actual ~19.68×22.68×0.81Full page
• 16x25x3Typical actual ~15.81×24.31×3Full page
• 20x20x3Typical actual ~19.75×19.75×3Full page
• 20x25x3Typical actual ~19.75×24.75×3Full page

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:

1. Width — one face dimension (example: 16).
2. Length — the other face dimension (example: 25).
3. 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.

How to measure a furnace filter