20x25x4 Filter Actual Size by Brand (and Why Some Aren't 4 Inches Deep)
Quick answer
There is no single 20x25x4. Filterbuy's is 19.5 × 24.5 × 3.63 in [S1], Honeywell's 20 x 25 media filter is 20 × 24⅞ × 4⅜ in [S2], Carrier's EZ Flex is about 19.9 × 24.7 × 4.5 in [S3], and Aprilaire lists its 20 x 25 x 4 filters at 20.6 × 26.63 × 4 in. [S5] Match the brand and depth of the filter you're taking out.
- A standard pleated 20x25x4 goes in a plain 4-inch slot. Filterbuy cuts its version to 3.63 in deep. [S1]
- Media cabinets from Honeywell, Carrier and Lennox take filters about 4⅜ to 4½ in deep, even when the box says 20x25x4. [S1] [S2] [S3] [S4]
- Aprilaire 210 and 213 filters are sold as 20 x 25 x 4, but Aprilaire's listed actual size is larger than 20 x 25. They're made for Aprilaire cabinets such as the 2210. [S5] [S6]
Actual sizes of filters sold as 20x25x4 (or for 20 x 25 cabinets)
Each row comes from the maker's own page or document unless it says otherwise.
| Filter | Sold as | Actual size (in) | Fits | Source |
|---|---|---|---|---|
| Filterbuy 20x25x4 (MERV 8, 11, 13) | 20x25x4 | 19.5 × 24.5 × 3.63 | Standard 4-inch slot | [S1] |
| Filtrete 20x25x4 | 20x25x4 | 19.88 × 24.63 × 4.31 (per Filterbuy, citing 3M's listing) | Measure first | [S1] |
| Honeywell FC100A1037 (MERV 11) / FC200E1037 (MERV 13) | 20 x 25 media filter | 20 × 24⅞ × 4⅜ | Honeywell F100/F200 20 x 25 media air cleaner | [S2] |
| Carrier EZ Flex EXPXXFIL0020 (MERV 10) / EXPXXFIL0320 (MERV 13) | 20 x 25 | 24.6875 × 19.9 × 4.5 assembled, ± 0.125 | Carrier EZXCAB and FILCAB 20 x 25 cabinets, plus the other cabinets Carrier lists | [S3] |
| Lennox X6673 (HCF20-11, MERV 11) | 20x25x5 | 19¾ × 24¾ × 4⅜ | Lennox HCC20-28 | [S4] |
| Aprilaire 210 (MERV 11) / 213 (MERV 13) | 20 x 25 x 4 | 20.6 × 26.63 × 4 | Aprilaire 1210, 1620, 2210, 2216, 3210, 4200 | [S5] [S6] |
Carrier gives its dimensions as length × width × depth. All other rows are width × length × depth or as the maker lists them.
Sort it out by depth
| Your old filter | What it probably is | Source |
|---|---|---|
| 3.75 in deep or less | A standard 20x25x4 | [S1] |
| 4.25 to 4.5 in deep | A media-cabinet filter, which Filterbuy sells as 20x25x5 whatever the old label says | [S1] |
| Expandable pleats that snap into black plastic end caps | Carrier EZ Flex. The FIL part number is media only; you reuse the end caps. | [S3] |
| 4 in deep with Aprilaire part number 210 or 213 on the frame | Aprilaire 20 x 25 cabinet filter | [S5] |
Why the same label means different filters
"20x25x4" is a nominal size, the rounded number you order by. Each maker cuts the filter to its own actual size, and Filterbuy says it undercuts its filters about half an inch on purpose so they slide in and seat. [S1] Media cabinets are a separate family. Honeywell, Carrier and Lennox build their cabinets around filters that are about 4⅜ to 4½ inches deep. [S2] [S3] [S4] Aprilaire's 20 x 25 filters are 4 inches deep but have a larger face than a standard filter, according to Aprilaire's own listings. [S5] [S6]
How to check yours
- Read the frame. The nominal size, and on cabinet filters the part number, is printed on it. If the old filter fit, buy the same size or part. [S8]
- Measure the depth. Filterbuy's rule: 3.75 inches or less is a standard 20x25x4; 4.25 to 4.5 inches is a media-cabinet filter. [S1]
- Look for a cabinet label. A boxed housing beside the furnace usually has the maker and model on it. The tables above list the filter each maker names for its 20 x 25 cabinets.
- No old filter? Measure the slot. The right filter covers the whole opening and lies flat. [S8]
Related: 20x25x1 vs 20x25x4 and Aprilaire 201 vs 213 vs 413.
Where to buy
We don't list prices because they change daily. Check the current price at the seller.
- AprilAire: 213 MERV 13 filter Official: Manufacturer store, for Aprilaire 20 x 25 cabinets. Check current price.
FAQ
What is the actual size of a 20x25x4 air filter?
It depends on the maker. Filterbuy's is 19.5 × 24.5 × 3.63 inches [S1]. Honeywell's 20 x 25 media filter is 20 × 24⅞ × 4⅜ inches [S2], and Aprilaire lists its 213 at 20.6 × 26.63 × 4 inches. [S5]
Is a 20x25x4 really 4 inches thick?
Usually not. Filterbuy's is 3.63 inches deep, and Filterbuy says some brands print 20x25x4 on filters that are about 4.38 inches deep. [S1] Aprilaire's 210 and 213 are listed at 4 inches deep. [S5] [S6]
Can I use a regular 20x25x4 in an Aprilaire 2210?
Aprilaire says the 2210 comes with a 213 filter and also takes the 210, 213CBN and 216. [S7] Aprilaire's listed size for the 213 (20.6 × 26.63 × 4 inches) doesn't match a standard 20x25x4, so stick with the Aprilaire numbers. [S5] [S1]
What 20 x 25 filter does a Carrier EZ Flex cabinet take?
Carrier lists EXPXXFIL0020 (MERV 10) and EXPXXFIL0320 (MERV 13) as media-only replacements, and EXPXXUNV0020 as the assembly with end caps. [S3]
How do I know which one I have?
Read the size and part number on the old filter's frame. If it fit well, buy the same thing. If it didn't, measure the slot. [S8]
What we could not verify
- Filtrete's 20x25x4 size comes from Filterbuy's comparison table, not from 3M's own page. We couldn't load 3M's product page to check it.
- Aprilaire's actual sizes are larger than the nominal 20 x 25. Aprilaire's product pages list them that way but don't explain why, so we haven't added an explanation.
- Bryant versions of the EZ Flex. Carrier's data sheet doesn't name Bryant cabinets, so we left them out of the table.
- We didn't measure any filters ourselves.
Sources
- [S1] 20x25x4 Air Filters, Filterbuy. Accessed 2026-10-24. Used for: Filterbuy actual size, depth table (including Filtrete per 3M's listing), depth rule of thumb.
- [S2] Honeywell Media Air Cleaners Professional Installation Guide (68-0239EF-12, Rev. 10-17), Honeywell International (PDF hosted by Build.com). Accessed 2026-10-24. Used for: FC100A1037/FC200E1037 size and cabinet.
- [S3] EXPX EZ Flex Expandable Air Filter, Sizes 016, 020, 024: Product Data, Carrier (PDF hosted by a Carrier distributor). Accessed 2026-10-24. Used for: EZ Flex 020 dimensions and tolerance, FIL vs UNV part numbers, MERV 10/13, cabinets it replaces.
- [S4] Healthy Climate HCC Media Air Cleaners product specifications (Form 210450, February 2026), Lennox Industries. Accessed 2026-10-24. Used for: X6673 nominal and actual size, HCC20-28.
- [S5] AprilAire 213 MERV 13 Air Filter, AprilAire. Accessed 2026-10-24. Used for: 213 nominal and actual size, compatible cabinets.
- [S6] AprilAire 210 MERV 11 Air Filter, AprilAire. Accessed 2026-10-24. Used for: 210 nominal and actual size, compatible cabinets.
- [S7] AprilAire 2210 Whole-House Air Purifier, AprilAire. Accessed 2026-10-24. Used for: 2210 ships with a 213 and takes 210, 213CBN and 216.
- [S8] Replace Air Filter Located in Furnace or Central Heat Pump Air Filter Slot, Building America Solution Center (PNNL, U.S. Department of Energy). Accessed 2026-10-24. Used for: Reuse the old filter's size if it fit; otherwise measure the slot; filter should lie flat.
Last checked 2026-10-24. Spot an error? Tell us and we'll recheck it against the source.