Furnace Filters
Best 24x25x4 Furnace Filter (2026): 4 Models Side by Side
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For the best 24x25x4 furnace filter, the Filter King leads this list: it is a MERV 8 pleated filter in a 4-pack with an actual size of 23.5 x 24.5 x 3.75 inches. The Filtrete adds MERV 11 filtration, while the Simply and Nordic Pure add MERV 8 options.
Starting out? See the main guide: Best Furnace Air Filters
Top picks at a glance
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Best OverallFilter King 24x25x4 Air Filter9.8 View on Amazon -
Runner-UpSimply 20x25x4 Air Filter9.5 View on Amazon -
Also GreatFiltrete 20x25x4 Air Filter9.5 View on Amazon -
Also GreatNordic Pure 20x25x49.2 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. Filter King 24x25x4 Air Filter | MERV 8 | 4-pack | — | — |
| 2. Simply 20x25x4 Air Filter | MERV 8 | — | — | — |
| 3. Filtrete 20x25x4 Air Filter | MERV 11 | — | — | — |
| 4. Nordic Pure 20x25x4 | MERV 8 | 2-pack | — | — |
Filter King 24x25x4 Air Filter
It pairs MERV 8 pleated filtration with a 4-pack and an actual size of 23.5 x 24.5 x 3.75 inches.
- MERV rating: MERV 8
- Pack size: 4-pack
Good for
- Buyers who want a 4-pack
- Buyers who want MERV 8 filtration
Skip it if
- You want a MERV rating over 8
- You want a filter lasting over 90 days
It is a MERV 8 pleated filter in a nominal 24x25x4 size, manufactured in the United States, with a pleated build and a slide-in mount. The 4-pack has an actual size of 23.5 x 24.5 x 3.75 inches and lasts up to 90 days. It fits air conditioners and furnaces with a rectangular slide-in shape.
Simply 20x25x4 Air Filter
It pairs MERV 8 pleated filtration with a 4-pack and an actual size of 19.5 x 24.5 x 3.6 inches.
- MERV rating: MERV 8
Good for
- Buyers who want a 4-pack
- Buyers who want MERV 8 filtration
Skip it if
- You want a MERV rating over 8
- You want filtration lasting over 3 months
It is a MERV 8 pleated filter in a nominal 20x25x4 size, with electrostatically charged synthetic media and a slide-in mount. The 4-pack has an actual size of 19.5 x 24.5 x 3.6 inches and lasts up to 3 months. It fits air conditioners, furnaces and heat pumps with a rectangular shape.
Filtrete 20x25x4 Air Filter
It pairs MERV 11 filtration with MPR 1000, a 4-pack and an actual size of 19.88 x 24.63 x 4.31 inches.
- MERV rating: MERV 11
Good for
- Buyers who want MERV 11 filtration
- Buyers who want a 12-month filter
Skip it if
- You want a MERV rating over 11
- You want a filter lasting over 12 months
It is a MERV 11 filter with MPR 1000 in a nominal 20x25x4 size, with pleated polypropylene media. The 4-pack has an actual size of 19.88 x 24.63 x 4.31 inches and changes at least once every 12 months. The Filtrete Smart App sets 90-, 180- or 365-day change reminders.
Nordic Pure 20x25x4
It pairs MERV 8 pleated filtration with a 2-pack and an actual size of 19.5 x 24.5 x 3.63 inches.
- MERV rating: MERV 8
- Pack size: 2-pack
Good for
- Buyers who want a 2-pack
- Buyers who want MERV 8 filtration
Skip it if
- You want a MERV rating over 8
- You want an MPR rating over 800
It is a MERV 8 pleated filter in a nominal 20x25x4 size, made in the USA with electrostatically charged synthetic pleated media. The 2-pack has an actual size of 19.5 x 24.5 x 3.63 inches, and MERV 8 is equivalent to MPR 800. It fits air conditioners and furnaces with a rectangular shape.
How to choose
Picking the best 24x25x4 furnace filter
Nominal size is the size on the box, while actual size is the measured size of the filter. The Filter King is the 24x25x4 pick, with an actual size of 23.5 x 24.5 x 3.75 inches. The Simply, Filtrete and Nordic Pure are 20x25x4 picks, with actual sizes of 19.5 x 24.5 x 3.6 inches, 19.88 x 24.63 x 4.31 inches and 19.5 x 24.5 x 3.63 inches. Match the actual size to your slot.
MERV ratings compared
MERV rates how well a filter captures particles, with a higher number meaning finer capture. The Filter King, Simply and Nordic Pure are MERV 8, while the Filtrete is MERV 11 with MPR 1000. Pick the rating that fits your system, and check that your system accepts that rating.
Packs and change intervals
Pack size decides how many filters one box holds: the Filter King, Simply and Filtrete come in 4-packs, while the Nordic Pure comes in a 2-pack. Change intervals differ too: the Filter King lasts up to 90 days, the Simply lasts up to 3 months, and the Filtrete changes at least once every 12 months. The Filtrete Smart App sets 90-, 180- or 365-day reminders. Match pack size and interval to your change routine.
FAQ
Which filter is actually 24x25x4?
The Filter King is the 24x25x4 pick, with an actual size of 23.5 x 24.5 x 3.75 inches. The Simply, Filtrete and Nordic Pure are 20x25x4 picks.
What MERV ratings do these filters have?
The Filter King, Simply and Nordic Pure are MERV 8, while the Filtrete is MERV 11 with MPR 1000.
When should each filter change?
The Filter King lasts up to 90 days, the Simply lasts up to 3 months, and the Filtrete changes at least once every 12 months.
Which filter has a smart app?
The Filtrete has the Smart App, which sets 90-, 180- or 365-day change reminders.
