20x20x1 air filter
A 20x20x1 filter is a nominal size. Five brands on this page list it between 19.5 x 19.5 x 0.75 and 19.75 x 19.75 x 0.75 inches, so measure your slot and compare it to the brand you plan to buy.
- Printed (nominal)
- 20" x 20" x 1"
- Actual, by brand
- 5 filters listed below
- Spread between brands
- 0.25" wide, 0.25" tall, 0.03" deep
- Face area (nominal)
- 2.78 sq ft
Actual size by brand
| Brand | Width | Height | Depth | Source |
|---|---|---|---|---|
| Filterbuy | 19.5" | 19.5" | 0.75" | [1] |
| Nordic Pure | 19.5" | 19.5" | 0.75" | [2] |
| AIRx (Discount Filters) | 19.5" | 19.5" | 0.75" | [3] |
| Filtrete | 19.62" | 19.62" | 0.78" | [4] |
| Aerostar | 19.75" | 19.75" | 0.75" | [5] |
MERV options
| Brand | MERV ratings sold at this size | Source |
|---|---|---|
| Filterbuy | 8, 11, 13 | [1] |
| Nordic Pure | 6, 7, 8, 10, 11, 12, 13, 14, 16 | [2] |
| AIRx (Discount Filters) | 7, 8, 11, 13 | [3] |
| Filtrete | 12 | [4] |
| Aerostar | 8 | [5] |
What MERV means: EPA, "What is a MERV rating?"
Listed prices
Prices change often. These are what each seller listed on the date shown.
| Seller | MERV | Pack | Price | Each | Checked | |
|---|---|---|---|---|---|---|
| Discount Filters | 8 | 4 | $54.95 | $13.74 | Oct 21, 2026 [3] | Check price |
| Nordic Pure | 8 | 6 | $53.99 | $9.00 | Oct 21, 2026 [2] | |
| Amazon (Filtrete) | 12 | 2 | $29.62 | $14.81 | Oct 21, 2026 [4] | Check price |
Printed size vs actual size
A 20x20x1 is square on paper, and the printed numbers are nominal. The real filter is a little under 20 inches on each side. Filterbuy, Nordic Pure and the AIRx line at Discount Filters all list 19.5 x 19.5 x 0.75 inches. Filtrete's Amazon listing gives 19.62 x 19.62 x 0.78, and Aerostar lists 19.75 x 19.75 x 0.75.
How much the brands differ
Across these five brands the face varies by 0.25 inches in each direction (19.5 to 19.75). Depth runs from 0.75 to 0.78 inches. Because the filter is square, it goes in either way round, so only the airflow arrow on the frame decides which face points where.
How to measure and what to buy
Check the size printed on your old filter, then measure the slot's width, height and depth. If the slot measures close to 19.75 x 19.75, a larger-cut brand such as Aerostar leaves less gap at the edges. If the slot is tight or nearer 19.5 x 19.5, choose one of the brands that lists 19.5. If you are between the two, the smaller filter is the safer buy, since an oversized one will not slide in.
Depth matters
The 1 inch filters on this page are 0.75 to 0.78 inches thick. A 1 inch slot cannot take a 2 or 4 inch filter, even with the same 20x20 face. Filtrete lists its MERV 12 version as MPR 1500.
Questions
What is the actual size of a 20x20x1 filter?
It depends on the brand. Filterbuy, Nordic Pure and AIRx list 19.5 x 19.5 x 0.75 inches, Filtrete lists 19.62 x 19.62 x 0.78, and Aerostar lists 19.75 x 19.75 x 0.75.
How much do 20x20x1 brands differ in size?
Across the five brands on this page, the face differs by up to 0.25 inches per side, and depth by up to 0.03 inches.
Will a 20x20x2 filter fit a 20x20x1 slot?
No. The 1 inch filters on this page are 0.75 to 0.78 inches deep, and a 1 inch slot has no room for a filter 2 or more inches deep.
Similar sizes
Not sure which you have? How to read and measure your filter.
Sources
- Filterbuy 20x20x1 air filter product page, read Oct 21, 2026
- Nordic Pure 20x20x1 air filter product page (actual size and price shown per MERV and box size), read Oct 21, 2026
- Discount Filters 20x20x1 furnace air filters, read Oct 21, 2026
- Filtrete 20x20x1 Air Filter, MERV 12, MPR 1500, 2 HVAC Filters (Amazon), read Oct 21, 2026
- Aerostar 20x20x1 Air Filter MERV 8, 12 Pack (Amazon), read Oct 21, 2026