Do Furnace Filters Need to be the Exact Size?

Learn how to measure furnace filters correctly and find out what size furnace filters you need for your system.

Do Furnace Filters Need to be the Exact Size?

Since air filters are usually sold for their nominal dimensions, it is essential to understand how to measure the air filter correctly. To do this, you will need a flashlight and a rigid measuring tape. Look inside the section of the oven where the air filter should go, there should be a 1″ filter track or opening where the air filter slides. You want the air filter to cover the duct opening.

Measure the height and width of the duct opening and allow it to overlap a bit if you have space. This will be the exact size you need to order for your new air filter. Please note that the air filter slot will be the actual size of the air filter, which is usually slightly smaller than its nominal size.

Oven filters

should fit properly, but you don't need to force them into position.

If you have to force the filter into its slot, it's probably too big. Forcing an incorrect filter size on a filter can cause it to bend, damage it, or reduce its ability to function properly. The filters are slightly smaller than their slot for easy replacement. Some HVAC units may need a filter with unique or unusual dimensions.

In these cases, it is necessary to request a custom filter.

Your oven filter

should fit snugly, but comfortably, in your oven. Having to bend and force the filter into the boiler is a clear indicator that the filter is too large. A restriction of air flow can also be observed by increasing the heating time of the boiler.

HVAC service companies typically offer air filter replacement services in addition to system repair and unit installation services. If your old air filter doesn't have the measurements printed on its side, you can measure the filter yourself. This size is usually on the filter just below the nominal size and is usually labeled as the actual size. To ensure that the next filter you buy is the right size for your system, you should measure the interior dimensions of the air filter inlet.

If your boiler has an air filter in the return vent, changing the filter is easy, since you can do it from inside your home. Please note that the sizes of the air conditioner and oven filters must be smaller than the measurements of the filter compartment. When purchasing an air filter online, it's important to know that they have two sizes: nominal and actual size. A higher MERV rating means that an air filter is more effective at removing smaller particles from the air.

For example, Home Depot primarily sells Honeywell brand air filters, while ACE Hardware primarily sells Filtrete. So, regardless of your situation, you can calculate the size of your oven's filter. The first (and easiest) way to find out what size your oven's filter is is to check your old one. Most filters will have their size printed directly on them in length x width x depth format.

Some of these measures include keeping a house clean and ventilated to reduce dust and pollen passing through the filter; a dirty or clogged up filter will be gray and covered with build-up, preventing air from easily passing through it; if you have to clog up an air filter to install it, try a different oven filter or a custom-sized one with a slightly smaller actual size.