20x25x1 air filter: actual size

Short answer: a filter sold as 20x25x1 is not 20 × 25 × 1 inches. Published actual sizes run from about 19.5 × 24.5 to 19.75 × 24.75 inches on the face, and about 0.75 to 0.81 inch thick, depending on the brand and even the product line.^{[1 2nd-hand 2 3 4 5 · Oct 23, 2026]}

Published actual sizes for 20x25x1

Brand / product family	Published actual size (in)	Source
Honeywell 1-inch (Ultra Efficiency MERV 13)	19.75 × 24.75 × 0.75	maker store specs^{[2 · Oct 23, 2026]}
Amazon Basics 1-inch (MERV 5 and MERV 8)	19.75 × 24.75 × 0.75	product titles, compiled^{[1 2nd-hand · Oct 23, 2026]}
Filtrete MPR 2200 / MERV 13	19.69 × 24.69 × 0.78	product listing^{[3 · Oct 23, 2026]}
Filtrete MPR 1000 / MERV 11	19.68 × 24.68 × 0.81	product title, compiled^{[1 2nd-hand · Oct 23, 2026]}
Filtrete MPR 1900 / MERV 13 (some pack sizes)	19.62 × 24.62 × 0.78	product titles, compiled^{[1 2nd-hand · Oct 23, 2026]}
Nordic Pure pleated	19.5 × 24.5 × 0.75	product listing^{[4 · Oct 23, 2026]}
Filter King pleated	19.5 × 24.5 × 0.75	product page^{[5 · Oct 23, 2026]}

Will a different brand fit my slot?

Usually yes. The brands above differ by about ¼ inch on each face. Switching from a 19.5 × 24.5 cut to a 19.75 × 24.75 cut means a snugger slide-in; going the other way means a slightly looser fit. A large visible gap around the frame is a sign of the wrong size.^{[1 2nd-hand · Oct 23, 2026]}
Even one brand varies. Filtrete's published sizes differ by product line, so if your slot is tight, check the actual size printed on the exact listing.^{[1 2nd-hand · Oct 23, 2026]}
25x20x1 is the same filter. The two face numbers can be printed in either order.^{[1 2nd-hand · Oct 23, 2026]}
Measured about 19¾ × 24¾ × ¾? That is a 20x25x1. Round the face numbers up to whole inches; a thickness near ¾ in is the 1-inch class.^{[5 · Oct 23, 2026]} Full method: nominal vs. actual filter size.
Not the same as 20x25x4 or 20x25x5. Deep media-cabinet filters are a different product; match the third number.

Picking a MERV rating

20x25x1 filters are widely sold in MERV 8, 11 and 13.^{[1 2nd-hand · Oct 23, 2026]} MERV comes from an ASHRAE test; a higher number captures more particles in the 0.3 to 10 micron test range. The EPA suggests using the highest rating your system's fan and filter slot can accommodate, and asking an HVAC technician if unsure.^{[6 · Oct 23, 2026]} Also see the 16x25x1 actual size page.

Sources: 1. FilterBySize, 20x25x1 actual size by brand (compiles makers' and sellers' published actual sizes; second-hand). 2. Honeywell Store, 20x25x1 Ultra Efficiency MERV 13. 3. Filtrete 20x25x1 MPR 2200 listing. 4. Nordic Pure 20x25x1 MERV 12 listing. 5. Filter King, 20x25x1 air filters. 6. US EPA, What is a MERV rating? Checked Oct 23, 2026.