Can I Use a 1-Inch Furnace Filter Instead of 4-Inch?

When it comes to furnace filters, the size matters. While a 4-inch thick filter is more efficient than a 1-inch filter, the correct size depends on the oven. If you measure the filter slot and it's large enough to accommodate the thicker filter, you can use it. However, if the slot is less than 4 inches wide, you won't be able to use that thickness.

To break it down further, let's compare 4-inch versus 1-inch oven filters. In general, a thicker filter has a clear advantage over a thin one in terms of longevity, air flow and maximum filtering potential. So, if it fits your oven, then a 4-inch air filter is better than a 1-inch air filter for improving air quality. At FilterBuy, the price difference between 1-inch and 4-inch air filters is usually just a few dollars.

Because a 4 inch filter lasts longer, it usually offers a better value. Virtually any HVAC professional will tell you that thicker filters work better than common 1-inch oven filters. Thicker filters, known as multimedia filters, are usually 4 to 5 inches thick compared to the ubiquitous 1-inch filters that can even be purchased at grocery stores. Forcing air to pass through a filter that is too thick or too dense will reduce efficiency dramatically.

This upgrade is money well spent, which will improve indoor air quality and help ease the burden placed on air conditioning systems by clogged air filters. If a certain amount of dirty air passes through both, the number of “unclogged” pores will be greater in a thicker filter than in a thinner one. Reducing the thickness by one inch shouldn't be a big problem; for example, you should be able to use a 4-inch filter instead of a 5-inch filter. On the other hand, you can use a 1-inch thick filter in compartments that can accommodate a deeper filter. If you try to use a 4-inch thick air filter for a system that is made for a 1-inch thick filter, the efficiency will actually be worse.

For comparison, a 4-inch thick filter will have approximately twice as many surface areas as a 2-inch thick filter. On the other hand, a thinner filter (1) will be more restrictive and will generate more air pressure on it. These 4-inch multimedia filters can have between 20 and 30 feet of surface area with their pleated (accordion) filter material. Disposable fiberglass filters are incredibly inexpensive, but are often not as high-quality as the other options. Oven filter sizes with a thickness or depth of one inch generally need to be changed more frequently. Personally, as an expert home inspector, I recommend installing a 4- to 5-inch media filter if possible for your system.

With more surface area to trap air contaminants, a 4-half air filter offers a longer lifespan than a 1-half air filter.

Janice Bollig
Janice Bollig

Food scholar. Freelance pop culture evangelist. Devoted bacon guru. Proud zombie aficionado. Extreme zombie ninja.

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