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Guide

Odd furnace filter sizes (when the label is not 16x25 or 20x20)

If the printed size on your filter is something like 14x25x1, 18x24x1, 16x30x1, 20x22x1, or 12x24x1 — not the big-box staples — buy that exact printed size. Big-box endcaps underserve these SKUs; specialty and online packs are often the reliable path. Typical actual cuts below come from our existing size pages (brand published dims), not invented numbers.

Quick answer

• Order the print — the whole-inch label on the frame is the shopping size. Do not order the fractional tape-measure reading.
• Axes can swap — 14x25x1 and 25x14x1 are the same face (we list the conventional smaller × longer × thickness form). Same idea for 12x24 vs 24x12, 16x30 vs 30x16, and so on.
• Measure when the slot is tight — brands cut the same label differently. See how to measure and the 1-inch actual-size chart.
• Big-box often thin — common endcaps stock 16x25, 20x20, 20x25, and 16x20 first. Odd nominals rotate in and out; check the size page for dated merchant tables instead of assuming Home Depot or Target has your pack tonight.

Odd size directory

Open the size page for brand actuals, MERV notes, and dated Buy tables. No pack prices are duplicated on this hub — dollars move nightly on the money pages.

High-search odd rectangles

• 14x25x1 — Typical published actual ~13.75 × 24.75 × 0.75 (Honeywell); Filtrete closer to ~13.81 / 13.68 face. Same SKU as 25x14x1.
• 18x24x1 — Typical published actual ~17.81 × 23.81 × 0.81 (Filtrete); Nordic Pure about 17.5 × 23.5 × 0.75 on our size page. Less common on big-box endcaps than 20x25.
• 16x30x1 — Typical published actual ~15.81 × 29.81 × 0.81 (Filtrete titles). Long face; confirm orientation before ordering a “close enough” 16x25.
• 20x22x1 — Typical published actual ~19.81 × 21.81 × 0.81 (Filtrete); Nordic Pure about 19.5 × 21.44 × 0.75. Not the same as 20x20 or 20x25.
• 12x24x1 — Typical published actual ~11.75 × 23.75 × 0.75 (Honeywell); Filtrete closer to ~11.68 / 11.69 face. Same SKU as 24x12x1.

More long-tail 1-inch sizes on this site

• 14x24x1 — Typical ~13.75 × 23.75 × 0.75 (Honeywell).
• 14x30x1 — Typical ~13.68 × 29.68 × 0.81 (Filtrete MPR 1000 listings on our size page).
• 20x23x1 — Typical ~19.68 × 22.68 × 0.81 (Filtrete). Easy to confuse with 20x22 or 20x24 — read the print.
• 20x24x1 — Typical ~19.75 × 23.75 × 0.75 (Honeywell). Not 20x25x1.
• 18x20x1 — Typical ~17.75 × 19.75 × 0.75 (Honeywell).
• 12x20x1 — Typical ~11.75 × 19.75 × 0.75 (Honeywell).
• 14x20x1 — Typical ~13.75 × 19.75 × 0.75 (Honeywell).
• 16x24x1 — Typical ~15.75 × 23.75 × 0.75 (Honeywell). Easy mix-up with the more common 16x25x1.
• 20x30x1 — Typical ~19.5 × 29.5 × 0.75 (Honeywell); Amazon Basics ~19.75 × 29.75 × 0.75 on our size page.

Square odd / less common faces

• 12x12x1 — Typical ~11.75 × 11.75 × 0.75 (Honeywell).
• 14x14x1 — Typical ~13.75 × 13.75 × 0.75 (Honeywell).
• 16x16x1 — Typical ~15.81 × 15.81 × 0.81 (Filtrete on our size page).
• 18x18x1 — Typical ~17.81 × 17.81 × 0.81 (Filtrete).
• 24x24x1 — Typical ~23.68 × 23.68 × 0.81 (Filtrete).
• 25x25x1 — Typical ~24.81 × 24.81 × 0.81 (Filtrete).

“Typical” here means the primary published cut we already document on that size page (usually Honeywell when listed, otherwise Filtrete). Brands still disagree by a few hundredths — open the size page before you force a tight slot.

Swapped-axis naming

Manufacturers and merchants print width × length in either order. A filter labeled 25x14x1 is the same shopping size as 14x25x1. We canonicalize to the form that matches common search (often shorter face first, then longer, then thickness). When you search a store, try both orders if the first returns nothing.

When big-box underserves

Home centers rotate odd SKUs. A 20x22x1 or 16x30x1 may be missing from the aisle even when 16x25x1 is stacked deep. That is a stocking problem, not a reason to buy the wrong face. Use the size page’s merchant table (specialty, brand store, or online multi-packs) and confirm the printed size matches your old filter. For MERV choice after you know the size: MERV 8 vs 11 vs 13. Pets / dander load: pets and allergies guide. Change interval by thickness: how often to change.

Measure tip for odd slots

1. Pull the old filter and read the print first.
2. If the print is gone, measure length, width, and thickness; round each face up to the nearest whole inch to get the shopping size.
3. Compare brand actuals on the size page — a Nordic Pure ~13.5 face vs Honeywell 13.75 on a 14x25x1 can feel different in a tight rail.
4. If no published cut matches your tape and slot, you may need a custom or different depth — that is not a reason to invent a nearby size.

How to measure a furnace filter

1-inch actual-size chart by brand

All listed sizes

Common sizes (for comparison)

Still looking for the everyday labels? Start here, then come back if the print does not match:

• 16x25x1 · MERV 13
• 20x20x1 · MERV 13
• 20x25x1 · MERV 13
• 16x20x1

Full policy: disclosure.