16x25x1 air filter: actual size by maker

Last updated: 2026-10-28

“16x25x1” is the nominal size, the rounded name printed on the frame. Its actual size by maker: Filterbuy 15.5x24.5x0.75 in, Glasfloss ZL 15-1/2 x 24-1/2 x 7/8 in. In decimals, the Glasfloss size is 15.5 x 24.5 x 0.875 in (our conversion of the fractions in its 2026 bulletin). Both makers cut the same length and width; only the depth differs.

16 x 25 x 1 in nominal

Filterbuy: 15.5x24.5x0.75 in actual. Glasfloss ZL: 15-1/2 x 24-1/2 x 7/8 in exact (15.5 x 24.5 x 0.875 in*).

Sources: Filterbuy 16x25x1 product page; Glasfloss Z-Line ZL product bulletin 6ZLINEZL (PDF), “ZL Standard Size Filters” table.

The size each maker cuts

Actual size by maker
Maker	Product	Nominal	Actual size as the maker prints it (in)	Source
Filterbuy	Model AFB16x25x1M8 (pleated, 1 in)	16x25x1	15.5x24.5x0.75	Filterbuy product page
Glasfloss	Z-Line ZL series (pleated)	16 x 25 x 1	15-1/2 x 24-1/2 x 7/8 (15.5 x 24.5 x 0.875*)	ZL product bulletin (PDF)

Filterbuy prints decimals and Glasfloss prints fractions. Decimal inches in brackets, marked *, are our conversion of the fractions Glasfloss prints. Glasfloss rates the ZL at MERV 10.

Depth is the one difference between the two makers' sizes. If your slot is tight front to back, compare the depth figure before you switch brands.

Deeper filters with the same face size

Some returns and filter cabinets take a 2 in or 4 in filter with the same face size. Glasfloss lists these exact sizes for its ZL series:

Deeper Glasfloss ZL filters with the same face size
Nominal (in)	Exact, Glasfloss ZL (in)
16 x 25 x 2	15-1/2 x 24-1/2 x 1-3/4 (15.5 x 24.5 x 1.75*)
16 x 25 x 4	15-1/2 x 24-1/2 x 3-3/4 (15.5 x 24.5 x 3.75*)

Source: Glasfloss Z-Line ZL product bulletin 6ZLINEZL (PDF), “ZL Standard Size Filters” table. A media cabinet made for one maker's filter may need that maker's part. See our AprilAire pages for two examples.

More 16x25x1 figures from the makers

Glasfloss lists 4.90 square feet of filter media for the 16 x 25 x 1 ZL, and gives its nominal size in millimeters as 406 x 635 x 26 mm.
Filterbuy calls the 16x25x1 “the most common furnace slot size in American homes, and the second most ordered filter size overall after the 20x20x1”.

Sources: Glasfloss Z-Line ZL product bulletin 6ZLINEZL (PDF), “ZL Standard Size Filters” table; Filterbuy 16x25x1 product page.

How to use these numbers

Read the nominal size printed on the frame of the filter you have now.
Measure the old filter's length, width and depth with a tape measure.
Compare your measurements with the actual sizes above. Pick the maker whose cut matches your old filter most closely.

Nordic Pure gives the same advice: “the actual size is the precise measurement of the filter, which is usually slightly smaller.” Read more on our nominal vs actual size page.

Sources

Filterbuy, 16x25x1 air filters product page (“Actual Size”, model AFB16x25x1M8): https://filterbuy.com/air-filters/16x25x1/, accessed 2026-10-27
Glasfloss, Z-Line ZL series product bulletin 6ZLINEZL, dated 3/10/26 (PDF): https://www.glasfloss.com/wp-content/uploads/2025/10/06baBro0326ZL.pdf, linked from https://www.glasfloss.com/product/zl/, accessed 2026-10-27
Nordic Pure, What is nominal size vs actual size?: https://www.nordicpure.com/what-is-nominal-size-vs-actual-size/, accessed 2026-10-27