18×24×1 air filter
Fits any system that takes an 18×24×1 filter. Actual size 17.75 × 23.75 × 0.75 inches, made to within 1/16 inch and measured before it ships. Made in the USA. Free shipping; you see your arrival date before you pay.
Grades and prices
| Grade | What it catches | Price per filter |
|---|---|---|
| Everyday (MERV 8) | Dust, lint and pollen. The right pick for most homes. | 4-pack $8.86 each, 6-pack $6.76 each, 12-pack $6.36 each |
| Allergy (MERV 11) | Adds pet dander and mold spores. For pets and allergy season. | 4-pack $12.40 each, 6-pack $9.47 each, 12-pack $8.90 each |
| Allergy + Smoke (MERV 13) | Adds smoke, smog and fine particles. For wildfire season and asthma. | 4-pack $13.73 each, 6-pack $10.48 each, 12-pack $9.85 each |
Subscribe and save 10%. Choose When you need it, timed to your local weather, air quality and household and billed per box, or Every few months, a box every 3, 6 or 12 months. Skip, change or cancel anytime.
Dimensions
- On the label
- 18 × 24 × 1 in
457 × 610 × 25 mm - Actual filter
- 17.75 × 23.75 × 0.75 in
451 × 603 × 19 mm - Face area
- 3 sq ft
0.28 m²
Where this size goes
In the 1,116 furnace and air handler models we've sized from manufacturer spec sheets:
- 5 air handlers take an 18×24×1 in the unit or its filter stand (First Co).
Examples: First Co 32UC0, First Co 32UCX, First Co 36UC0, First Co 37UC0. Look up your model.
How often to change it
| Household | Everyday (MERV 8) | Allergy (MERV 11) | Allergy + Smoke (MERV 13) |
|---|---|---|---|
| A typical home | 3 months | 3 months | 2.5 months |
| With pets | 2 months | 2 months | 7 weeks |
| Pets and allergies, or smoke season | 6 weeks | 6 weeks | 5 weeks |
Heating and cooling season, pollen and wildfire smoke shorten these; mild spring and fall weeks stretch them. More on timing.
How long a pack lasts
| Pack | Typical home | With pets | Everyday, a month |
|---|---|---|---|
| 4-pack | 11 months | 7 months | $3.22 |
| 6-pack | 17 months | 11 months | $2.39 |
| 12-pack | 33 months | 22 months | $2.31 |
On a subscription we send each box when your home needs it, so you never store more than you use.
Questions about 18×24×1 filters
Is 18×24×1 the real size?
Not quite, and that's normal. 18×24×1 is the size on the label. The filter itself measures 17.75 × 23.75 × 0.75 in (451 × 603 × 19 mm), a little smaller so it slides into the slot. We make ours to within 1/16 inch of that.
How much does an 18×24×1 filter cost?
In a 6-pack, Everyday (MERV 8) is $6.76, Allergy (MERV 11) is $9.47, Allergy + Smoke (MERV 13) is $10.48 per filter. A 12-pack costs a little less per filter, and subscribing saves another 10%. Free shipping in the US.
How often should I change an 18×24×1 filter?
About every 3 months in a typical home with Everyday or Allergy, and every 2.5 months with Allergy + Smoke. With pets, closer to every 2 months. Heating and cooling season, pollen and smoke fill it faster, so "When you need it" times each swap to your home's weather and household instead of the calendar.
Can I use a 16×24×1 instead?
No. Even an inch matters. A smaller filter leaves a gap that lets dusty air slip around it, and a bigger one won't slide in. Order the exact size printed on your old filter's edge. If it's a size no store carries, we make any custom size, priced like the next standard size up.
Is 24×18×1 the same as 18×24×1?
Yes. Manufacturers list the two face sides in either order. What matters is the airflow arrow on the frame: point it toward the furnace or air handler, away from the room.
What if it doesn't fit?
Tell us within 30 days and we'll send a new one free, and you keep the first. That's our fit guarantee.