furnacefiltersize.com

Find the furnace filter size to order.

The number printed on the cardboard is the size you order. The tape measure will read smaller. That is on purpose. Your furnace model does not pick the filter.

Affiliate buttons appear after a result, not as hero buttons. We do not stock filters.

Four jobs this site does

Tape measureOld filter in hand, or an empty slot. Two different rounding rules. Cabinet stickerGAPAAXCC, 2210, EZXCAB — the cabinet model is the key, not the furnace dataplate. MERV 13 in a 1-inch slot?Draft page. Finder will not select MERV 13 in 1-inch unless you know the blower. Landlord pack1–20 doors, mixed sizes, one CSV. Not a resident-benefits subscription.

Nominal vs actual — a short example

Filters are sold by the printed (nominal) size and cut smaller so they slide in. Filterbuy’s own 20x25x1 cut is 19.50 × 24.50 × 0.75. A Filtrete 20x25x1 listing they compared in July 2026 was 19.68 × 24.68 × 0.81. Amazon Basics 20x25x1: 19.75 × 24.75 × 0.75. Same label, three cuts. Full chart.

Filterbuy production actuals (their cut, not an industry standard). Retrieved 31 Aug 2026 from the Filterbuy size chart.
Nominal	Filterbuy actual	Typical slot
16x20x1	15.5 × 19.5 × 0.75	Return grille
16x25x1	15.5 × 24.5 × 0.75	Common furnace slot
20x20x1	19.5 × 19.5 × 0.75	Filterbuy: “most common US size”
20x25x1	19.5 × 24.5 × 0.75	Air handler / large slot
16x25x4	15.5 × 24.5 × 3.63	Media cabinet
20x25x4	19.5 × 24.5 × 3.63	Media cabinet — not an Aprilaire 213

Photo needed: Label vs tape on a real 20x25x1 — Brad’s photos, week 1.

Not a stock HVAC photo. Placeholders until the hardware-store run is shot.

Three facts before you order

Printed size on the cardboard is the ordering size. Tape reads about 0.25–0.5 in under nominal (Filterbuy size chart; their 20x25x1 is 19.50 × 24.50 × 0.75).
Furnace model number does not set filter size. The filter cabinet model does, when a media cabinet exists. Otherwise the slot or grille does. (Atomic Filters Carrier guide, July 2026; Filterbuy FAQ says the same.)
Thickness is hardware, not preference. 1-inch will not fill a 4-inch cabinet; 4-inch will not enter a 1-inch slot.

Also: MERV 8 / 11 / 13 · odd and custom · who writes this.