Common Home Air Filter Sizes & Brands Guide
Choosing the right air filter comes down to two things: the size that fits your system and the efficiency rating that matches your air. This guide walks through the most common residential filter sizes, the brands worth knowing, and how to pair both with your home so every replacement is a quick, confident swap.
The most common residential filter sizes
Most forced-air furnaces and central AC systems in North American homes use a standard 1″ filter in one of a handful of nominal sizes. The ones we ship most often include:
- 16x25x1 and 20x25x1 — two of the most widespread sizes in the country
- 16x20x1 and 20x20x1 — common in smaller systems and return grilles
- 14x25x1 and 14x20x1 — frequent in older or compact air handlers
One important note: the size printed on a filter is the nominal size, not the exact measurement. A 16x25x1 filter usually measures closer to 15.5 x 24.5 x 0.75 inches so it slides in and out without binding. That's normal — buy by the nominal number printed on your current filter, not by a tape measure reading down to the fraction.
How to find your size
You have two easy options. First, pull your current filter and read the size stamped on the cardboard frame — it's printed as length x width x depth. Second, if the print has worn off, measure the filter slot or the old frame and round to the nearest common size. Our complete guide to measuring a furnace filter walks through it step by step, and if the numbers feel confusing, navigating the maze of HVAC filter sizes clears up the common mix-ups.
Thickness matters as much as length and width
That last number — the depth — is easy to overlook, but it changes how a filter performs. Standard 1″ filters fit the most systems, while deeper 4″ and 5″ media (think 16x25x4, 20x25x4, or 20x25x5) pack far more pleated surface area. More surface area means lower pressure drop, better efficiency, and a longer service life — but only if your system has a cabinet or rack built for the deeper size. Never force a thick filter into a 1″ slot. For a full breakdown, see 1-inch vs. 2-inch vs. 4-inch filters, and browse the full range of sizes in our air filters collection.
The brands worth knowing
Remember the Filter has been an authorized dealer since 2006, and a few names come up again and again:
- AAF Flanders — a major American manufacturer behind lines like NaturalAire and EZ Flow. Learn more in our AAF Flanders filter guide.
- Koch Filter — American-made pleated and commercial media, a longtime favorite of facility managers.
- Filtrete (3M) — a familiar retail brand that rates its filters on the MPR scale rather than MERV.
- Honeywell and Trion Air Bear — common in whole-house media cabinets that use thicker 4″ and 5″ filters.
Don't forget the MERV rating
Size gets the filter in the slot; MERV determines what it captures. MERV (Minimum Efficiency Reporting Value) is the universal ASHRAE scale, where 1–16 covers residential and light-commercial filters. As a rule of thumb:
- MERV 8 — solid everyday protection against dust, lint, and pollen
- MERV 11 — a step up for homes with pets or mild allergies
- MERV 13 — captures finer particles like smoke and is often chosen for asthma or allergy sufferers
Keep in mind that a higher MERV also restricts airflow more, so match the rating to what your blower can handle. Our MERV 8 vs. 11 vs. 13 home guide helps you pick without starving your system.
Odd sizes and custom fits
Not every home takes a standard size. Older houses, additions, and some high-efficiency cabinets need in-between or oversized filters. When a stock size won't do, our custom filters are cut to your exact dimensions — the custom air filter sizes guide explains how to order the perfect fit.
Frequently asked questions
What is the most common home air filter size?
16x25x1 and 20x25x1 are among the most common 1″ sizes in North American homes, but every system is different. Always confirm by reading the size printed on your current filter's frame.
Are the nominal and actual filter sizes the same?
No. The nominal size printed on the frame is rounded up; the actual size is usually about half an inch smaller so the filter fits without jamming. Order by the nominal number.
Which MERV rating should I buy?
MERV 8 works well for most homes. Move up to MERV 11 for pets or mild allergies, or MERV 13 for fine particles — as long as your HVAC system is rated for the added airflow resistance.
What if my size isn't listed?
Order a made-to-measure filter from our custom collection. Measure the old frame, round to the nearest quarter inch, and we'll build it to spec. Free shipping applies on orders over $50.