20×20×4 air filter
Fits any system that takes a 20×20×4 filter. Actual size 19.75 × 19.75 × 3.75 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 $19.95 each, 6-pack $15.23 each, 12-pack $14.32 each |
| Allergy (MERV 11) | Adds pet dander and mold spores. For pets and allergy season. | 4-pack $27.93 each, 6-pack $21.32 each, 12-pack $20.04 each |
| Allergy + Smoke (MERV 13) | Adds smoke, smog and fine particles. For wildfire season and asthma. | 4-pack $30.93 each, 6-pack $23.61 each, 12-pack $22.19 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
- 20 × 20 × 4 in
508 × 508 × 102 mm - Actual filter
- 19.75 × 19.75 × 3.75 in
502 × 502 × 95 mm - Face area
- 2.78 sq ft
0.26 m²
Where this size goes
A 4" filter goes in a whole-house media cabinet, a box mounted beside the furnace or air handler that holds a thick filter instead of a thin one in a slot. None of the furnaces and air handlers we've sized from spec sheets use it in the unit itself, so check the grille or slot you pull the old filter from.
How often to change it
| Household | Everyday (MERV 8) | Allergy (MERV 11) | Allergy + Smoke (MERV 13) |
|---|---|---|---|
| A typical home | 6 months | 6 months | 5 months |
| With pets | 4 months | 4 months | 3.5 months |
| Pets and allergies, or smoke season | 3 months | 3 months | 2.5 months |
A 4" filter has far more pleat surface than a 1" filter, so it lasts much longer. 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 | 2 years | 17 months | $3.32 |
| 6-pack | 3 years | 25 months | $2.54 |
| 12-pack | 6 years | 50 months | $2.39 |
On a subscription we send each box when your home needs it, so you never store more than you use.
Questions about 20×20×4 filters
Is 20×20×4 the real size?
Not quite, and that's normal. 20×20×4 is the size on the label. The filter itself measures 19.75 × 19.75 × 3.75 in (502 × 502 × 95 mm), a little smaller so it slides into the slot. We make ours to within 1/16 inch of that.
How much does a 20×20×4 filter cost?
In a 6-pack, Everyday (MERV 8) is $15.23, Allergy (MERV 11) is $21.32, Allergy + Smoke (MERV 13) is $23.61 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 a 20×20×4 filter?
About every 6 months in a typical home with Everyday or Allergy, and every 5 months with Allergy + Smoke. With pets, closer to every 4 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.
Will a 20×20×1 fit where my 20×20×4 goes?
A 1" filter is thinner, so it would slide in but leave a gap that lets air go around it. Stay with 20×20×4 for a 4" cabinet.
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.