20x20x1 Filter Actual Size by Brand (and the 20x20 Media Filters That Aren't 1-Inch)
Quick answer
A 20x20x1 isn't really 20 × 20 × 1. Filterbuy cuts it to 19.5 × 19.5 × 0.75 in, and a Filtrete MPR 2200 20x20x1 is listed at 19.69 × 19.69 × 0.78 in. Order by the nominal size printed on your old filter. [S1] [S2]
- The undercut is deliberate: Filterbuy says it's clearance so the filter slides in and seats without bowing. [S1]
- Some "20 × 20" filters are thick media-cabinet filters. Honeywell's FC100A1011 is 20 × 19¾ × 4⅜ in [S3], and Lennox's 20x20x5 HCF14 filters are also 20 × 19¾ × 4⅜ in. [S4]
- If your old filter fit well, buy the same nominal size. If it didn't, measure the slot. [S5]
20x20x1 actual sizes
| Filter | Actual size (in) | Source |
|---|---|---|
| Filterbuy 20x20x1 (MERV 8/11/13, Odor Eliminator) | 19.5 × 19.5 × 0.75 | [S1] |
| Filtrete 20x20x1 MPR 2200 (MERV 13), 4-pack | 19.69 × 19.69 × 0.78 (the same listing's "assembled" dimensions say 19.72 × 19.72) | Retailer listing [S2] |
Expect small differences between brands, which is why a filter that fit snugly can feel loose or tight after you switch.
"20 × 20" filters that aren't 1-inch
If your old filter came out of a boxed cabinet beside the furnace, it's probably one of these rather than a 20x20x1.
| Filter | For cabinet | Nominal | Actual size (in) | Source |
|---|---|---|---|---|
| Honeywell FC100A1011 (MERV 11) / FC200E1011 (MERV 13) | Honeywell F100/F200 20 × 20 media air cleaner | 20 x 20 | 20 × 19¾ × 4⅜ | [S3] |
| Lennox HCF14-11 (box filter X0585) | HCC08-21, HCC14-23 (air handlers) | 20 x 20 x 5 | 20 × 19¾ × 4⅜ | [S4] |
| Lennox HCF14-13 (MERV 13) | HCC14-23 | 20 x 20 x 5 | 20 × 19¾ × 4⅜ | [S4] |
Measuring the right way
The DOE Building America guide says the dimensions are usually printed on the old filter's cardboard frame. If that filter fit correctly, buy the same length and width. [S5] If it didn't, measure the slot. A properly sized filter covers the whole duct opening and lies flat, never at an angle. [S5] When you shop, compare the actual dimensions, not just the nominal size. [S5]
Where to buy
We don't link to specific sellers here yet. Search for the exact part number or size on this page at a retailer you trust, compare the listed actual dimensions, and check the current price. We don't list prices because they change daily.
FAQ
What is the actual size of a 20x20x1 air filter?
It depends on the brand. Filterbuy's is 19.5 × 19.5 × 0.75 inches [S1], and a Filtrete MPR 2200 is listed at 19.69 × 19.69 × 0.78 inches. [S2]
My filter measures 19½ x 19½. What size do I order?
Order 20x20x1. Filterbuy cuts its 20x20x1 to 19½ × 19½ × ¾ inches. [S1]
Is a Honeywell 20x20 media filter the same as a 20x20x1?
No. Honeywell's 20 x 20 media filter (FC100A1011 or FC200E1011) is 20 × 19¾ × 4⅜ inches and fits the F100/F200 media air cleaner. [S3]
How often should I change a 20x20x1?
Lennox says to change standard 1-inch disposable filters every three months, or more often with allergies, pets or dust. [S6]
Which MERV rating should I use?
EPA recommends at least MERV 13, or as high as your system fan and filter slot can handle. [S7]
What we could not verify
- Filtrete's size comes from a Home Depot Canada listing, not 3M's own spec sheet. Other Filtrete 20x20x1 listings we saw in search results gave slightly different numbers, so we didn't include them.
- Other brands' 20x20x1 dimensions (Honeywell 1-inch, Nordic Pure, store brands). We'll add them once we've checked each brand's own listing.
Sources
- [S1] 20x20x1 Air Filters — Filterbuy. Accessed 2026-10-24. Used for: Filterbuy actual size; why filters are undercut.
- [S2] 3M Filtrete 20 x 20 x 1 Air Filter, MERV 13, MPR 2200 (4-Pack) — The Home Depot Canada. Accessed 2026-10-24. Used for: Filtrete MPR 2200 actual size.
- [S3] 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: FC100A1011/FC200E1011 size.
- [S4] Healthy Climate HCC Media Air Cleaners product specifications (Form 210450, February 2026) — Lennox Industries. Accessed 2026-10-24. Used for: HCF14-11/HCF14-13 sizes and cabinets.
- [S5] 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.
- [S6] Air Filters — Lennox Residential. Accessed 2026-10-24. Used for: Change 1-inch filters every three months.
- [S7] What is a MERV rating? — U.S. EPA. Accessed 2026-10-24. Used for: MERV 13 recommendation.
Last checked 2026-10-24. Spot an error? Tell us and we'll recheck it against the source.