Replacement 20x20x4 air filters for homes, offices, and commercial HVAC systems. This collection covers every MERV rating we stock: fiberglass MERV 1–4, pleated MERV 8, MERV 10, MERV 11, and hospital-grade MERV 13.

20+ years in filtration 4.8 from 1,000+ reviews

47 products

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  • WAREHOUSE DEAL 20x20x4 AAF Flanders VariCel 2+ High Capacity No Header MERV 14 3184626-805 (4 Filters)
    MERV 14Up to $76.05 off
    AAF Flanders

    WAREHOUSE DEAL 20x20x4 VariCel 2+ High Capacity No Header MERV 14 3184626-805

    Only 1 left
    $429.88
    $429.88 $505.93
    Case of 4 $107.47/filter
  • Koch Multi-Pleat HT 20x20x4 MERV 8 high-temperature pleated panel filter with 24-gauge aluminized steel frame and microfiberglass media for 500F applications
    MERV 8
    Koch

    20x20x4 Multi-Pleat HT High Temperature MERV 8

    $554.70
    $554.70
    Case of 6 $92.45/filter
  • Koch MicroMAX PL4S Header Style 25x20x4 MERV 11 4-inch synthetic-media plastic-frame side-access minipleat filter
    MERV 11
    Koch

    20x20x4 MicroMAX PL4S Header Style MERV 11

    $414.15
    $414.15
    Case of 3 $138.05/filter
  • Koch MicroMAX PL4S Header Style 25x20x4 MERV 11 4-inch synthetic-media plastic-frame side-access minipleat filter
    MERV 13
    Koch

    20x20x4 MicroMAX PL4S Header Style MERV 13

    $420.36
    $420.36
    Case of 3 $140.12/filter
  • Koch MicroMAX PL4S Header Style 25x20x4 MERV 11 4-inch synthetic-media plastic-frame side-access minipleat filter
    MERV 14
    Koch

    20x20x4 MicroMAX PL4S Header Style MERV 14

    $426.54
    $426.54
    Case of 3 $142.18/filter
  • Koch MicroMAX PL4S Header Style 25x20x4 MERV 11 4-inch synthetic-media plastic-frame side-access minipleat filter
    MERV 15
    Koch

    20x20x4 MicroMAX PL4S Header Style MERV 15

    $439.74
    $439.74
    Case of 3 $146.58/filter
  • Koch MicroMAX PL4S 20x20x4 MERV 11 4-inch synthetic-media plastic-frame box-style minipleat filter
    MERV 11
    Koch

    20x20x4 MicroMAX PL4S Box Style MERV 11

    $408.81
    $408.81
    Case of 3 $136.27/filter
  • Koch MicroMAX PL4S 20x20x4 MERV 13 4-inch synthetic-media plastic-frame box-style minipleat filter
    MERV 13
    Koch

    20x20x4 MicroMAX PL4S Box Style MERV 13

    $414.93
    $414.93
    Case of 3 $138.31/filter
  • Koch MicroMAX PL4S 20x20x4 MERV 14 4-inch synthetic-media plastic-frame box-style minipleat filter
    MERV 14
    Koch

    20x20x4 MicroMAX PL4S Box Style MERV 14

    $421.05
    $421.05
    Case of 3 $140.35/filter
  • Koch MicroMAX PL4S 20x20x4 MERV 15 4-inch synthetic-media plastic-frame box-style minipleat filter
    MERV 15
    Koch

    20x20x4 MicroMAX PL4S Box Style MERV 15

    $434.07
    $434.07
    Case of 3 $144.69/filter
  • Koch MicroMAX FM Single Header 20x20x4 MERV 11 galvanized metal frame 4-inch minipleat filter
    MERV 11
    Koch

    20x20x4 MicroMAX FM Single Header MERV 11

    $803.16
    $803.16
    Case of 3 $267.72/filter
  • Koch MicroMAX FM Single Header 20x20x4 MERV 13 galvanized metal frame 4-inch minipleat filter
    MERV 13
    Koch

    20x20x4 MicroMAX FM Single Header MERV 13

    $834.93
    $834.93
    Case of 3 $278.31/filter
  • Koch MicroMAX FM Single Header 20x20x4 MERV 14 galvanized metal frame 4-inch minipleat filter
    MERV 14
    Koch

    20x20x4 MicroMAX FM Single Header MERV 14

    $836.16
    $836.16
    Case of 3 $278.72/filter
  • Koch MicroMAX 20x20x4 MERV 11 galvanized-metal-frame 4-inch extended-surface minipleat filter
    MERV 11
    Koch

    20x20x4 MicroMAX Galvanized Metal Frame MERV 11

    $588.36
    $588.36
    Case of 3 $196.12/filter
  • Koch MicroMAX 20x20x4 MERV 11 beverage-board-frame 4-inch extended-surface minipleat filter
    MERV 11
    Koch

    20x20x4 MicroMAX Beverage Board Frame MERV 11

    $316.77
    $316.77
    Case of 3 $105.59/filter
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Commercial & facilities

Need 20x20x4 by the pallet?

Volume pricing on any size or MERV, plus recurring delivery schedules. We handle facilities and commercial orders daily and can usually match or beat distributor pricing.

Request a quote 1-866-469-8556 Talk to a filter expert

20x20x4 HVAC, Furnace & AC Filters

Replacement 20x20x4 air filters for homes, offices, and commercial HVAC systems. This collection covers every MERV rating we stock: fiberglass MERV 1–4, pleated MERV 8, MERV 10, MERV 11, and hospital-grade MERV 13. Free shipping on orders over $50.

If your rack is labeled 20x20x4, any filter here will fit. Actual dimensions vary slightly by manufacturer—check the product page for exact specs. Need a non-standard size? Our custom filters cut to 1/8″ precision.

Which MERV Rating Should I Choose?

  • MERV 1–4 (fiberglass) — Lowest cost. Protects your blower and coil from debris but won't improve air quality. Best for rentals and monthly-change schedules.
  • MERV 8 (pleated) — Residential and light-commercial standard. Captures dust, pollen, lint, and mold spores.
  • MERV 10–11 — Captures pet dander, finer particulate, and some bacteria. Recommended for pets, allergies, and facilities pursuing better IAQ.
  • MERV 13 — Hospital-grade. Captures smoke, bacteria, virus carriers, and most airborne allergens. ASHRAE and CDC recommend MERV 13 where the HVAC system can support it.

Not sure? Take our MERV quiz or call 1-866-469-8556.

How Often Should I Change a 20x20x4 Filter?

4″ media cabinets hold dramatically more filter media than 1″ or 2″ filters, so they run longer between changes—typically every 6–12 months. Fewer changes per year, less labor, and typically lower total cost of ownership. A 6-month or annual subscription matches the natural changeout cycle.

Why Buy From RememberTheFilter.com

  • Trusted brands — AAF Flanders, Koch, and our own PrimeShield line, built by manufacturers we've partnered with for nearly two decades.
  • Filter Fit Guarantee — if it doesn't fit as expected, we'll make it right.
  • Free shipping over $50 to the lower 48, subscription discounts up to 10%, commercial & bulk pricing available.