FilterBySize Furnace and AC filter sizes, actual dimensions, MERV

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20x20x4 air filter: actual size, MERV, and price

A 20x20x4 is a four-inch-class media cartridge for a dedicated filter cabinet — Honeywell F100, F150, and F200 20×20 housings and similar — not a one-inch furnace slot. Buy the printed size 20x20x4. Do not substitute a 20x20x1. The panel is smaller than 20 inches on each face, and actual depth varies more by brand than it does on 1-inch filters.

Common published actuals: Honeywell FC100/FC200 replacements about 19.94 × 19.75 × 4.38 (also printed 19.875 square × 4.375), Filtrete deep-pleat 19.75 or 19.88 square × 4.31, Nordic Pure about 19.5 × 19.5 × 3.63. That depth gap is why some Honeywell cabinet replacements are also sold as 20x20x5. A 20x20x5 SKU is not automatically the same cartridge as a 20x20x4. Measure the old cartridge.

Actual size by brand

These numbers are copied from manufacturer or merchant product copy, not from a competitor size chart. Thickness is the fit problem on this size: 4-inch actual depth is not one number. A 3.63-inch “20x20x4” will rattle in a Honeywell 4-3/8-inch cabinet; a 4.38-inch cartridge will not slide into a 3-5/8-inch slot.

Brand Nominal Published actual (in.) Source
Honeywell FC100A1011 (MERV 11) and FC200E1011 (MERV 13) 20x20x4 19.94 × 19.75 × 4.38 (19-15/16 × 19-3/4 × 4-3/8) Amazon Resideo FC100A1011 listing “Actual Filter Size: 19-15/16" × 19-3/4" × 4-3/8"”; product-dimensions field 19.94 × 19.75 × 4.38. Filters Fast OEM spec for FC100A1011 and FC200E1011 prints the same 19-15/16 × 19-3/4 × 4-3/8
Honeywell FC100A1011 / FC200E1011 (some Honeywell merchants) 20x20x4 19.875 × 19.875 × 4.375 (19-7/8 × 19-7/8 × 4-3/8) Air Quality Honeywell Store product specs (“Exact Dimensions: 19 7/8 × 19 7/8 × 4 3/8”). Same SKUs; two published figures. Measure if the cabinet is tight
BestAir HW2020-8R (Honeywell F100/F200 replacement) 20x20x4 19.75 × 19.75 × 4.375 (19¾ × 19¾ × 4⅜) Amazon B08HCBH2J7 product description “actual 19¾ × 19¾ × 4⅜”. No public cart price on that listing this check
Filtrete 20x20x4 MPR 1900 / MERV 13 20x20x4 19.75 × 19.75 × 4.31 3M Filtrete product page “Actual filter size is: 19.75 in × 19.75 in × 4.31 in”; Amazon B0DCGRLXXW title and dimensions field
Filtrete 20x20x4 MPR 1550 / MERV 12 20x20x4 19.88 × 19.88 × 4.31 Amazon B09RQC7ML5 title “Actual Size 19.88×19.88×4.31 in” and product-dimensions field
Filtrete 20x20x4 MPR 1000 / MERV 11 20x20x4 19.88 × 19.88 × 4.31 Amazon B09RQBH847 title “Act. Size 19.88×19.88×4.31 in”; bullet “exact dimensions are 19.88 in × 19.88 in × 4.31 in”. Same-SKU product-dimensions field lists 20 × 20 × 4
Nordic Pure 20x20x4 pleated 20x20x4 Approximately 19.5 × 19.5 × 3.63 (19½ × 19½ × 3⅝) JB Tools listings for 20x20x4M8-6, 20x20x4M13-1, and 20x20x4M13-6. Nordic Pure’s own copy says a Honeywell 4-3/8-inch-depth cartridge is their 20x20x5, not this 20x20x4

If you currently run Nordic Pure 20x20x4 (~3.63 deep) and switch to Honeywell FC100/FC200 or Filtrete deep-pleat (~4.31–4.38 deep), you are not swapping like-for-like. The reverse is also true: a 3.63-inch pack will not fill a Honeywell F100/F200 cabinet. Measure the old cartridge. Full method: how to measure.

Amazon Basics: no 20x20x4 SKU with a printed actual turned up in this check, so that brand is omitted rather than guessed.

MERV 8 vs 11 vs 13 (facts only)

MERV is ASHRAE 52.2, as summarized by EPA. Higher MERV captures a larger share of smaller particles. It also adds resistance. EPA says to pick at least MERV 13 or as high a rating as your system fan and filter slot can accommodate, and to ask an HVAC technician if you are unsure. A 4-inch MERV 13 is not HEPA. We do not claim health outcomes.

MERV EPA average capture efficiency (particle size) Typical 20x20x4 use
8 ≥20% of 1.0–3.0 µm; ≥70% of 3.0–10.0 µm Common pleated 4-inch replacement when the cabinet manual does not call for higher (Nordic Pure 20x20x4M8; BestAir HW2020-8R for Honeywell cabinets)
11 ≥20% of 0.30–1.0 µm; ≥65% of 1.0–3.0 µm; ≥85% of 3.0–10.0 µm Honeywell FC100A1011 OEM media; Filtrete MPR 1000 4-inch deep-pleat is commonly labeled MERV 11
13 ≥50% of 0.30–1.0 µm; ≥85% of 1.0–3.0 µm; ≥90% of 3.0–10.0 µm Honeywell FC200E1011 OEM media; Filtrete MPR 1900 4-inch. Confirm the air handler can take the extra pressure drop. Not HEPA

Source: U.S. EPA, “What is a MERV rating?”, last updated 14 Jan 2026. Filtrete also prints an MPR number; MPR is 3M’s scale, not MERV. Compare MERV to MERV. Filtrete MPR 1550 20x20x4 is labeled MERV 12 (price row below); EPA’s table still uses the 8 / 11 / 13 steps shown here.

Pack prices checked 30 Aug 2026

These are public shelf/cart prices we recorded on 30 Aug 2026. They are not live. Shipping, subscribe-and-save, and store-only deals will move them. Per-filter math is pack price ÷ count, rounded to the cent. Nordic Pure 20x20x4 rows are the 3.63-inch-depth SKU, not Honeywell 4-3/8-inch cabinet media.

Listing MERV Pack Price that day Per filter Merchant
Nordic Pure 20x20x4 pleated (3-5/8 actual depth) 8 6 $107.99 $18.00 JB Tools
Filtrete 20x20x4 MPR 1000 Allergen Defense 11 2 $47.99 $24.00 Amazon
Honeywell FC100A1011 (Amazon reseller 2-pack) 11 2 $73.84 $36.92 Amazon
Honeywell FC100A1011 11 5 $245.00 $49.00 Air Quality Honeywell Store
Honeywell FC100A1011 11 4 $200.00 $50.00 Air Quality Honeywell Store
Honeywell FC100A1011 11 2 $115.00 $57.50 Air Quality Honeywell Store
Honeywell FC100A1011 11 1 $63.95 $63.95 Filters Fast
Honeywell FC100A1011 11 1 $67.50 $67.50 Air Quality Honeywell Store
Filtrete 20x20x4 MPR 1550 Ultra Allergen 12 2 $59.99 $30.00 Amazon
Nordic Pure 20x20x4 pleated (3-5/8 actual depth) 13 6 $143.99 $24.00 JB Tools
Nordic Pure 20x20x4 pleated (3-5/8 actual depth) 13 1 $33.29 $33.29 JB Tools
Filtrete 20x20x4 MPR 1900 Premium Allergen 13 2 $72.07 $36.04 Amazon
Honeywell FC200E1011 13 5 $360.00 $72.00 Air Quality Honeywell Store
Honeywell FC200E1011 13 4 $290.00 $72.50 Air Quality Honeywell Store
Honeywell FC200E1011 13 1 $79.95 $79.95 Filters Fast
Honeywell FC200E1011 13 2 $165.00 $82.50 Air Quality Honeywell Store
Honeywell FC200E1011 13 1 $94.50 $94.50 Air Quality Honeywell Store

Observed range that day: Nordic Pure 20x20x4 (3.63-inch depth) about $18/filter at MERV 8 in a 6-pack and $24 at MERV 13 in a 6-pack — that SKU is not a Honeywell F100/F200 cartridge. For ~4.3-inch-depth media: Filtrete about $24 (MERV 11 2-pack), $30 (MERV 12 2-pack), $36 (MERV 13 2-pack); Honeywell FC100A1011 MERV 11 about $37–$68/filter depending on pack and merchant; Honeywell FC200E1011 MERV 13 about $72–$95/filter. Target Filtrete A-15120860 and Target BestAir A-90978106 product pages loaded a bot check with no public cart price, so those pack prices are omitted rather than guessed. Amazon BestAir HW2020-8R had no featured offer. Amazon Basics has no 20x20x4 SKU in this check.

Where to buy

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No ranking. Stock and price change. If the slot is an odd fraction that none of these actual sizes match, measure first — that is not a 20x20x4 SKU. A 20x20x1 is not a substitute. A 20x20x5 may be the Honeywell 4-3/8-inch cabinet cartridge under a different nominal; it is not a 3.63-inch 20x20x4.

Sources (accessed 30 Aug 2026)