16x25x1 air filter: actual size

Short answer: a filter sold as 16x25x1 is not 16 × 25 × 1 inches. Published actual sizes run from about 15.5 × 24.5 to 15.75 × 24.75 inches on the face, and about 0.75 to 0.81 inch thick. There is no single industry standard, so the exact cut depends on the brand.^{[1 2nd-hand 2 · Oct 22, 2026]}

Published actual sizes for 16x25x1

Brand / product family	Published actual size (in)	Source
Amazon Basics 1-inch	15.75 × 24.75 × 0.75	product listing, compiled^{[1 2nd-hand · Oct 22, 2026]}
Honeywell 1-inch (current MERV 11 and 13)	15.75 × 24.75 × 0.75	maker store specs, compiled^{[1 2nd-hand · Oct 22, 2026]}
Accumulair Platinum (AirFilters.com)	15.75 × 24.75 (1-inch class)	product title, compiled^{[1 2nd-hand · Oct 22, 2026]}
Filtrete 1-inch	15.69 × 24.69 × 0.81 (some SKUs 0.78)	listings, compiled^{[1 2nd-hand · Oct 22, 2026]}
Nordic Pure	15.5 × 24.5 × 0.75	listings and spec sheets, compiled^{[1 2nd-hand · Oct 22, 2026]}
AIRx (Discount Filters)	15.5 × 24.5 × 0.75	product specifications^{[3 · Oct 22, 2026]}
Honeywell CF108A1625 MERV 8 (discontinued)	15.5 × 24.5 × 0.90	older cut; current Honeywell 1-inch SKUs differ^{[1 2nd-hand · Oct 22, 2026]}

Will a different brand fit my slot?

Usually yes. The spread between brands is about ¼ inch on each face. A 15.5 × 24.5 filter is a slightly looser fit than a 15.69 × 24.69 one; either can be correct, but a large visible gap around the frame is not.^{[1 2nd-hand · Oct 22, 2026]}
Thickness is the tighter limit. The 1-inch class is roughly ¾ to 0.81 in thick. Don't force a thicker filter into a 1-inch rack.^{[1 2nd-hand · Oct 22, 2026]}
Measured 15¾ × 24¾ × ¾? That is a 16x25x1. Round the face numbers up to whole inches; a thickness near ¾ in means the 1-inch class.^{[1 2nd-hand · Oct 22, 2026]}
Not the same as 16x25x4 or 16x25x5. Deep media-cabinet filters are a different product; match the third number (or the cabinet's model number).^{[1 2nd-hand · Oct 22, 2026]}
Don't order the actual size as a custom size. Retail filters are sold under the nominal label 16x25x1.^{[1 2nd-hand · Oct 22, 2026]}

Picking a MERV rating

16x25x1 filters are commonly sold in MERV 8, 11 and 13. MERV comes from an ASHRAE test; a higher number captures more particles in the 0.3 to 10 micron test range. The EPA suggests the highest rating your system fan and filter slot can accommodate, and checking with an HVAC technician if unsure.^{[4 · Oct 22, 2026]} See the nominal vs. actual size page for the full MERV capture table.

Sources: 1. FilterBySize, How to measure a furnace filter (compiles makers' and sellers' published actual sizes for 16x25x1; second-hand). 2. ClariSelect, HVAC filter sizing: nominal vs. actual. 3. Discount Filters, 16x25x1 product specifications. 4. US EPA, What is a MERV rating? Checked Oct 22, 2026.