Furnace Filters
Best 18x24x1 Furnace Filter (2026): 5 Picks Compared
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For an 18x24x1 furnace filter, the Filtrete 18x24x1 leads with MERV 5 filtration at MPR 300 in a 6-pack of pleated filters. The Filter King and Simply picks add MERV 8 options, while the UBeesize and REAIR picks add washable, reusable designs. Check the actual size on each pick before ordering, since nominal size and actual size differ here.
Starting out? See the main guide: Best Furnace Air Filters
Top picks at a glance
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Best OverallFiltrete 18x24x1 Air Filter9.8 View on Amazon -
Runner-UpFilter King 18x24x1 Air Filter MERV9.6 View on Amazon -
Also GreatSimply 18x24x1 Air Filter9.3 View on Amazon -
9.3 View on Amazon -
Also GreatREAIR 18x24x1 Air filter Pro Kit9.2 View on Amazon
Compare the specs
Ranked on pack size from each listing, plus how many buyers have rated it. A dash (—) means we could not confirm that figure from the listing.
| Pick | MERV rating | Pack size | Weight | Warranty |
|---|---|---|---|---|
| 1. Filtrete 18x24x1 Air Filter | MERV 5 | 6-pack | — | — |
| 2. Filter King 18x24x1 Air Filter MERV | MERV 8 | 6-pack | — | — |
| 3. Simply 18x24x1 Air Filter | MERV 8 | — | — | — |
| 4. UBeesize 18x24x1 Reusable Electrostatic Air Filter HVAC | MERV 8 | — | — | 2-year |
| 5. REAIR 18x24x1 Air filter Pro Kit | MERV 8 | — | — | 5-year |
Filtrete 18x24x1 Air Filter
It pairs MERV 5 filtration with MPR 300 in a pleated 6-pack sized for standard furnace and air conditioner systems.
- MERV rating: MERV 5
- Pack size: 6-pack
Good for
- Buyers who want a 6-pack of pleated filters
- Owners of furnace and air conditioner systems using 18x24x1 filters
Skip it if
- You want a MERV rating above 5
- You want to buy a single filter only
Each filter measures 17.81 x 23.81 x 0.81 inches against an 18x24x1 nominal size, and the box holds 6 filters. Filtrete 3-in-1 technology pulls in and traps particles while air flows through. Change the filter at least once every 90 days, and the Filtrete Smart App sets 30-, 60- or 90-day reminders.
Filter King 18x24x1 Air Filter MERV
It gives MERV 8 filtration in a 6-pack of pleated filters that last up to 90 days before replacement.
- MERV rating: MERV 8
- Pack size: 6-pack
Good for
- Buyers who want MERV 8 filtration in a 6-pack
- Owners of air conditioner and furnace systems
Skip it if
- You want a MERV rating above 8
- You want a 2-pack instead of a 6-pack
The pleated design captures more particles and extends the lifetime of the filter without impacting air flow. Installation is open, slide, and close, and the actual size is 17.5 x 23.5 x .75 inches against an 18 x 24 x 1 nominal size. Change it every 30 to 90 days for 1 inch filters.
Simply 18x24x1 Air Filter
It offers Merv 8 filtration in a 4-pack with a pleated, electrostatically charged synthetic media filter.
- MERV rating: MERV 8
Good for
- Buyers who want Merv 8 filtration in a 4-pack
- Owners of air conditioner, furnace, or heat pump systems
Skip it if
- You want a MERV rating above 8
- You want a 6-pack instead of a 4-pack
The box holds 4 air filters plus an installation guide, and the filter lasts up to 3 months. It uses 100% American components, including recycled materials.
UBeesize 18x24x1 Reusable Electrostatic Air Filter HVAC
It brings a washable, reusable MERV 8 filter with an aluminum frame and pleated layers.
- MERV rating: MERV 8
- 2-year warranty stated
Good for
- Buyers who want a washable, reusable filter
- Owners of furnace, HVAC, or air conditioner systems
Skip it if
- You want a disposable filter
- You want a filter you never wash
Wash it with water and a little detergent, let it dry naturally, and reinstall it, cleaning every 3 months. The actual size is 17.44 x 23.46 x 0.82 inches, and it carries a 2-year manufacturer warranty.
REAIR 18x24x1 Air filter Pro Kit
It packs a washable, reusable MERV 8 filter with a honeycomb structure and a snap-on frame.
- MERV rating: MERV 8
- 5-year warranty stated
Good for
- Buyers who want a washable filter with a frame
- Owners of air cleaner, furnace, or heat pump systems
Skip it if
- You want a disposable filter
- You want a filter you never wash
ASHRAE 52.2 pressure drop is 0.38 inches w.g. at 1367 CFM and 0.54 inches w.g. at 1750 CFM. Wash it every 30 to 60 days, install it in minutes with the snap-on frame, and the box holds 2 filters, 1 frame, and a storage case.
How to choose
Nominal size versus actual size
The picks here carry 18x24x1 nominal sizes, yet the actual sizes differ: 17.81 x 23.81 x 0.81 inches for the Filtrete, 17.5 x 23.5 x .75 inches for the Filter King, and 17.44 x 23.46 x 0.82 inches for the UBeesize. Measure your filter slot before ordering and match the actual size, not the nominal size, so the filter seats in the slot.
What a MERV rating means
MERV rates how well a filter captures particles, with a higher number meaning finer capture. This list spans MERV 5 for the Filtrete and MERV 8 for the Filter King, Simply, UBeesize, and REAIR picks. Pick the rating that fits your system, and check that your system accepts that rating.
Disposable or washable filters
The Filtrete, Filter King, and Simply picks are disposable filters changed every 30 to 90 days or up to 3 months. The UBeesize washes with water and detergent every 3 months, and the REAIR washes every 30 to 60 days with a snap-on frame. Match the upkeep style to the handling you prefer.
FAQ
When should I replace an 18x24x1 furnace filter?
The Filtrete changes at least once every 90 days, the Filter King changes every 30 to 90 days, and the Simply lasts up to 3 months. The UBeesize washes every 3 months and the REAIR washes every 30 to 60 days.
What is the difference between nominal size and actual size?
Nominal size is the rounded size on the box, while actual size is the measured size of the filter. The Filtrete measures 17.81 x 23.81 x 0.81 inches and the UBeesize measures 17.44 x 23.46 x 0.82 inches, so match the actual size to your slot.
Which MERV rating do these furnace filters have?
The Filtrete is MERV 5, and the Filter King, Simply, UBeesize, and REAIR picks are MERV 8. A higher MERV number means finer particle capture.
