20x20x1 Air Filter: Actual Size, MERV Picks, and Where to Buy
Nominal size (what you shop by)
20x20x1
- Actual size
- 19.5 x 19.5 x 0.75
- Replace
- Typically every 1 to 3 months
Actual size shown is from Filterbuy. Other brands can differ by up to about a quarter inch.
Check three things before you buy
- The thickness (the last number) matches your filter slot.
- The size matches the label on your current filter, or your measurements.
- The MERV rating is one your system's manual allows.
Picking a MERV rating
- MERV 8: Standard household filtering. Catches dust, pollen, and lint.
- MERV 11: A step up for pets and allergies. A common upgrade.
- MERV 13: Catches much smaller particles. Check your system's manual first, because tighter filters can restrict airflow.
Models that use a 20x20x1 filter
- Goodman ARUF37C14
- Goodman ASPT49C14
- Daikin DV37PTCC14
- Goodman AMST42CU1300
- Trane TAM4A0B42S31SD
- American Standard GAM5B0B36M31SB
- York AP42CX21
- York AE36CX21
Buy the right one
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Common questions
What is the actual size of a 20x20x1 filter?
Commonly 19.5 x 19.5 x 0.75, but it varies slightly by brand.
What is the difference between nominal and actual size?
The nominal size (20x20x1) is the rounded name used when you shop. The actual size is usually a little smaller so the filter slides in easily, and it can vary slightly by brand. Check the package for the exact measurements.
How often should I replace it?
Typically every 1 to 3 months. Replace sooner with pets, allergies, or heavy use, and follow your system's manual.
Source: manufacturer documentation
Not sure of your size? How to measure your filter.