1-Inch Pleated● In stock
21×21×1Air Filter
Actual size: 20.5″ × 20.5″ × 0.75″
Fits any 21x21x1 slot or return grille. Order by the size printed on your old filter.
Fits any 21x21x1 slot or return grille. Order by the size printed on your old filter.
- Free shipping $100+
- Fit guarantee
- Picked by HVAC techs
Choose your protection level
Pack size (bigger packs save more)
21x21x1 · MERV 11 · 3-Pack$44.97$28.99
Or subscribe: $9.49/filter delivered, never think about it againMERV 11 · 3-Pack
$28.99
Common questions about 21x21x1
What is the actual size of a 21x21x1 filter?+
The nominal size printed on the frame is 21x21x1, but the filter actually measures 20.5" × 20.5" × 0.75". That undercut is intentional, it slides into your filter track without binding. Order by the nominal size printed on your old filter.
Which MERV rating should I pick for a 21x21x1?+
MERV 8 handles everyday dust. MERV 11 is our most popular, it captures pet dander and pollen. MERV 13 adds smoke, bacteria, and virus-carrier capture, and it's fine in modern systems (post-1995 blowers). When in doubt, call us, a real HVAC tech answers.
How often should I change a 21x21x1 filter?+
Every 30-90 days. Monthly if you have pets or allergies; every 2-3 months otherwise. Our subscription handles the schedule for you.
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