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The Goodman GR9S80 gas furnace uses one of 4 filter sizes, depending on cabinet width (or model) and return location: 16x25, 14x24, 20x25, 24x24 (per the Goodman document cited on this page). The page's table shows which size applies to each cabinet and return.
Verified from manufacturer doc 80% AFUE single-stage upflow/horizontal furnace (R-32 era)
| Model | Minimum filter size(s) |
|---|---|
| GR9S800403A / 0603A | (1) 16 x 25 (side) or (1) 14 x 24 (bottom) |
| GR9S800604B / 0804B | (1) 16 x 25 (side or bottom) |
| GR9S800805C | (1) 16 x 25 (side or bottom) – see note |
| GR9S801005C | (2) 16 x 25 (side) or (1) 20 x 25 (bottom) |
| GR9S801205D | (2) 16 x 25 (side) or (1) 24 x 24 (bottom) |
Note: use 2 x 16x25 (side) or 20x25 (bottom) if connected to a cooling unit over 4 tons. Downflow GD9S80 sizes are listed separately in the same sheet.
General guidance (not from this manual): check monthly and replace 1-in. filters every 1–3 months, or follow the filter maker's guidance and your owner's manual.
Pull the old filter and read the size printed on its frame. Nominal sizes are rounded up: a 15.5 x 24.5 in. filter is sold as 16 x 25.
Your furnace manual lists the filter's dimensions, not its MERV rating. Higher-MERV filters restrict more air. Manufacturers such as Carrier recommend keeping the clean-filter pressure drop under 0.2 in. w.c. (ideally under 0.1). Lennox warns that an over-restrictive filter can trip the high limit in winter and freeze the coil in summer. If you want MERV 11–13, a 4-in. media cabinet is the usual route. Ask an HVAC tech to check static pressure. Nominal sizes are rounded: a filter labeled 16 x 25 x 1 actually measures about 15.5 x 24.5 x 0.75.
SS-GR9S80/GD9S80 specification sheet, Minimum Filter Sizes
Last checked 2026-10-21. Manufacturers revise documents. If your unit's label disagrees, trust the label.
The Goodman GR9S80 gas furnace uses one of 4 filter sizes, depending on cabinet width (or model) and return location: 16x25, 14x24, 20x25, 24x24 (per the Goodman document cited on this page). The page's table shows which size applies to each cabinet and return. GR9S800403A / 0603A – (1) 16 x 25 (side) or (1) 14 x 24 (bottom); GR9S800604B / 0804B – (1) 16 x 25 (side or bottom); GR9S800805C – (1) 16 x 25 (side or bottom) – see note; GR9S801005C – (2) 16 x 25 (side) or (1) 20 x 25 (bottom); GR9S801205D – (2) 16 x 25 (side) or (1) 24 x 24 (bottom).
General guidance (not from this manual): check monthly and replace 1-in. filters every 1–3 months, or follow the filter maker's guidance and your owner's manual.
Filter sizes are nominal (rounded). A filter sold as 16 x 25 x 1 actually measures about 15.5 x 24.5 x 0.75 in. Buy by the nominal size printed on the frame.
SS-GR9S80/GD9S80 specification sheet, Minimum Filter Sizes (https://apps.goodmanmfg.com/brochures/files/68ed1f1dc3ab0SS-GR9S80_GD9S80-R32.pdf), last checked 2026-10-21.