FilterBySize Furnace and AC filter sizes, actual dimensions, MERV

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18x18x1 air filter: actual size, MERV, and price

Printed size 18x18x1 — actual about 17.81 × 17.81 × 0.81 (varies by brand). Pick a pack below.

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Our pickNordic Pure 18x18x1 pleated (official via Awin)MERV 8 · Pack of 6$55.99$9.33 per filterLowest verified price per filter (MERV 8–11): $9.33 each, checked 16 OctBuy at Nordic Pure

Match & price

Looking for MERV 13 only? See the 18x18x1 MERV 13 hub (Nordic Pure 2- to 24-pack direct, plus Nordic Pure and Filtrete MPR 1900 6-packs on Amazon; prices checked 16 Oct).

Full answer

A 18x18x1 is a one-inch-class square furnace or AC filter. Buy the printed size 18x18x1. The panel is smaller than 18 inches on each face — Filtrete closer to 17.68 × 17.68 × 0.81 or 17.81 × 17.81 × 0.81, and Nordic Pure about 17.75 × 17.75 × 0.75. Do not substitute 18x20x1 or 18x24x1 — 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
Filtrete 18x18x1 MPR 1000 / MERV 11 18x18x1 Title: 17.68 × 17.68 × 0.81; dimensions field also 17.81 × 17.81 × 0.81 Amazon B07FP5X4GW — two figures on the same listing; B005GZ8PEC 4-pack title and dimensions field print the same pair; measure if the slot is tight
Filtrete 18x18x1 MPR 1000 / MERV 11 2-pack 18x18x1 17.81 × 17.81 × 0.81 Amazon B0FST2RGV8 title “Actual Size 17.81 × 17.81 × 0.81 in”; product-dimensions field lists 17.81 × 17.81 × 0.81
Filtrete 18x18x1 MPR 700 / MERV 8 18x18x1 17.81 × 17.81 × 0.81 Amazon B0DLPTXMN2 title “Actual Size 17.81 × 17.81 × 0.81 in”; product-dimensions field lists 17.81 × 17.81 × 0.81
Filtrete 18x18x1 MPR 1900 / MERV 13 18x18x1 17.81 × 17.81 × 0.78 Amazon B07FNQWZSC title “Act Size 17.81×17.81×0.78 in”; product-dimensions field lists 17.81 × 0.78 × 17.81
Nordic Pure 18x18x1 pleated 18x18x1 Approximately 17.75 × 17.75 × 0.75 (17¾ × 17¾ × ¾) JB Tools listings for Nordic Pure 18x18x1M8-6, 18x18x1M8-2, 18x18x1M13-6, and 18x18x1M13-2

We did not find a Honeywell Store 18x18x1 1-inch SKU (MERV 8/11/13 4-pack or 12-pack) that publishes actual dimensions, so that brand is omitted rather than guessed. Nearby listed Honeywell 1-inch sizes include 18x20x1. We did not find an Amazon Basics 18x18x1 listing that publishes an actual-size field, so that brand is omitted rather than guessed. If you currently run Nordic Pure (~17.75 square) and switch to Filtrete (~17.68 or 17.81 square), expect a slightly different 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 18x18x1 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 18x18x1: about $8.40/filter at MERV 8 in a Nordic Pure 6-pack, $10.50 at MERV 13 in a Nordic Pure 6-pack, with 2-packs costing more per filter ($14.62 MERV 8; $15.75 MERV 13). Honeywell Store product URLs for 18x18x1 MERV 8/11/13 4-packs and 12-packs returned 404, so those rows are omitted rather than guessed. Walmart Filtrete product pages were not used for this check. Amazon Filtrete pages were used for actual-size fields, not for this price table. Amazon Basics had no published 18x18x1 actual-size listing. Factory cart pack prices for listed MERV 8 and MERV 13 2/6-packs were verified 15 Sep 2026 from nordicpure.com (pick MERV and pack on the factory page). A 18x18x1 is not a 18x20x1 or a 18x24x1.

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 a 18x18x1 SKU. A 18x20x1 or 18x24x1 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 18x18x1 MERV 8/11/13 4-pack and 12-pack product URLs returned 404; no published actual for this size
  • Amazon Filtrete B07FP5X4GW, B005GZ8PEC, B0FST2RGV8, B0DLPTXMN2, and B07FNQWZSC titles (actual-size fields). No Amazon Basics 18x18x1 actual-size listing found
  • JB Tools Nordic Pure 18x18x1M8-2 ($29.24), 18x18x1M8-6 ($50.39), 18x18x1M13-2 ($31.49), and 18x18x1M13-6 (17.75×17.75×0.75, $62.99)