FilterBySize Furnace and AC filter sizes, actual dimensions, MERV

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18x20x1 air filter: actual size, MERV, and price

Printed size 18x20x1 — actual about 17.75 × 19.75 × 0.75 (varies by brand). Pick a pack below.

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Our pickNordic Pure 18x20x1 pleated (official via Awin)MERV 8 · Pack of 24$190.99$7.96 per filterLowest verified price per filter (MERV 8–11): $7.96 each, checked 16 OctBuy at Nordic Pure

Match & price

Full answer

An 18x20x1 is a one-inch-class rectangle furnace or AC filter. Buy the printed size 18x20x1. The panel is smaller than 18 by 20 inches — commonly 17.75 × 19.75 × 0.75, with Filtrete closer to 17.81 × 19.81 × 0.81 or 17.68 × 19.68 × 0.81 and Nordic Pure about 17.5 × 19.5 × 0.75.

Full answer

Same panel, swapped axes: 20x18x1. We treat 18x20x1 as the canonical label. Order 18x20x1. Do not substitute 16x20x1 or 20x20x1 — those are different printed sizes.

Actual dimensions by brand

Actual size by brand

These numbers are copied from manufacturer or merchant product copy, not from a competitor size chart. Thickness is part of the fit: 1-inch racks take ~¾ inch media.

Brand Nominal Published actual (in.) Source
Honeywell 1-inch Standard/High/Ultra Efficiency (MERV 8, 11, and 13) 18x20x1 17.75 × 19.75 × 0.75 Honeywell Store product specs
Filtrete 18x20x1 MPR 1000 / MERV 11 18x20x1 17.81 × 19.81 × 0.81 Amazon B0FST3KJB3 title “Actual Size 17.81 × 19.81 × 0.81 in” and product-dimensions field
Filtrete 18x20x1 MPR 1000 / MERV 11 (some listings) 18x20x1 17.68 × 19.68 × 0.81 Amazon 4-pack titles “Actual Size 17.68 × 19.68 × 0.81 in” — different figure than the 2-pack SKU; measure if the slot is tight
Filtrete 18x20x1 MPR 1900 / MERV 13 18x20x1 17.81 × 19.81 × 0.78 Amazon B0F9LTKG2W title “Act Size 17.81x19.81x0.78 in”; same-SKU product-dimensions field lists 19.81 × 17.81 × 0.81
Filtrete 18x20x1 MPR 700 / MERV 8 18x20x1 17.81 × 19.81 × 0.81 Amazon B0DKZ428BF title “Actual Size 17.81 × 19.81 × 0.81 in”
Nordic Pure 18x20x1 pleated 18x20x1 Approximately 17.5 × 19.5 × 0.75 (17½ × 19½ × ¾) JB Tools listing for Nordic Pure 18x20x1M8-24 and 18x20x1M13-24

We did not find an Amazon Basics 18x20x1 listing that publishes an actual-size field, so that brand is omitted rather than guessed. If you currently run Nordic Pure (~17.5 × 19.5) and switch to Honeywell (17.75 × 19.75) or Filtrete (~17.81 × 19.81), expect a snugger slide-in. Filtrete’s published actuals also disagree with each other by SKU. Measure the old filter if the slot is tight. Full method: how to measure.

MERV 8 vs 11 vs 13 (EPA facts)

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 1-inch MERV 13 is not HEPA. We do not claim health outcomes.

MERV EPA average capture efficiency (particle size) Typical 18x20x1 use
8 ≥20% of 1.0–3.0 µm; ≥70% of 3.0–10.0 µm Common pleated replacement when the manual does not call for higher
11 ≥20% of 0.30–1.0 µm; ≥65% of 1.0–3.0 µm; ≥85% of 3.0–10.0 µm Mid-grade 1-inch pleat (Filtrete MPR 1000 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 Higher-efficiency 1-inch; confirm the furnace/air handler can take the extra pressure drop

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.

Where these prices came from

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.

Observed range that day for ordinary pleated 18x20x1: about $7.16–$13.49/filter at MERV 8 in multi-packs, $14.66–$15.99 at MERV 11, $10.12–$17.99 at MERV 13, with 4-packs costing more per filter than 12- or 24-packs. Walmart Filtrete product pages returned a bot check, so those pack prices are omitted rather than guessed. Amazon Filtrete pages were used for actual-size fields, not for this price table. Amazon Basics had no published 18x20x1 actual-size listing. A Nordic Pure 18x20x1 MERV 8 12-pack page timed out, so that pack is omitted rather than guessed; the JB Tools 24-pack is the reseller snapshot. Nordic Pure Buy buttons go through Awin to nordicpure.com. Factory cart pack prices for listed MERV 8 and MERV 13 24-packs were verified 15 Sep 2026 from nordicpure.com.

Where to buy (all stores)

Where to buy

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 an 18x20x1 SKU. A 16x20x1 or 20x20x1 is not a substitute.

Sources

Sources (accessed 30 Aug 2026)

  • EPA MERV table: epa.gov/indoor-air-quality-iaq/what-merv-rating (updated 14 Jan 2026)
  • Honeywell Store 18x20x1 MERV 8/11/13 pack pages (prices and 17.75×19.75×0.75; each Buy link re-pointed to its exact MERV/pack page, prices re-checked live 28 Sep 2026)
  • Amazon Filtrete B0FST3KJB3, B0F9LTKG2W, and B0DKZ428BF titles (actual-size fields); 4-pack titles with 17.68×19.68×0.81. No Amazon Basics 18x20x1 actual-size listing found
  • JB Tools Nordic Pure 18x20x1M8-24 ($171.89) and 18x20x1M13-24 (17.5×19.5×0.75, $242.99)