How to Find the Right HVAC Filter Size

An HVAC system is a big investment for your home. You want to protect your investment, and regular HVAC maintenance is the best way to ensure your system is running at top efficiency. One of the best things you can do for your HVAC system is to regularly check and change the air filter.

Fortunately, changing the air filter is one of the maintenance tasks you can do on your own, provided you know what size and type you need. If you don’t, shopping for air filters can be overwhelming.

Of course, you can always contact a professional to change your air filter. But if you prefer to do it yourself, here’s how to find the right HVAC filter size.

Why Does the Air Filter Size Matter?

If your air filter isn’t properly fitted, you won’t get the best results for your HVAC system. A filter that’s too big won’t fit in the slot and cutting it to size isn’t a good practice. This leaves gaps that can allow contaminants and air to pass through, defeating the purpose of having a filter in the first place.

Similarly, if your air filter is too small, you’ll have the same problem. You don’t want to deal with poor air quality or high energy bills from inefficiency, so be sure you’re getting the right filter size for your HVAC system.

Look at Your Existing Air Filter

For ease, many HVAC filter companies print the size on the front or side of the filter. The filter’s size listing shows the length, width, and depth in inches.

For example, your air filter may measure “20x20x1,” which indicates the size is 20 inches in length by 20 inches in width by one inch in depth. With this information, you can find an air filter replacement that has the same dimensions. Filter sizes are standardized, so you shouldn’t have trouble finding the right replacement.

Measure It Yourself

While most air filters often have the size printed, some don’t. If yours doesn’t have a size listed, you can measure it yourself and do some simple math to figure out the length, width, and depth of your replacement.

The air filter dimensions are usually a little larger than the actual size of the air filter. So, if you have an air filter that measures 20 inches by 20 inches by one inch, your actual measurements may be 20.5 inches in length, 20.5 inches in width, and .5 inches in depth. You don’t need to find the smaller size – just round up to the nearest inch.

Measure Air Register or Air Filter Slot

Sometimes checking the size or measuring the actual air filter isn’t an option, like if your HVAC system is missing the air filter completely. You can measure the slot that the filter fits into to get the right measurement.

The air filter slot will measure out to the same size as the actual filter, however, so it will be a little smaller than the replacement size you need. This is like measuring the air filter directly – the measurements will need to be rounded up to the nearest inch.

Where Is the Air Filter Located?

The air filter on your HVAC system should be found on the return air intake. You can find this area near the return duct where it enters into your HVAC system, and there should be a plate that covers the air filter slot.

Some HVAC systems don’t have air filters in the air handling unit. The air filter is likely near the return vent on the inside of your home. If you can access the vent, you can change the filter yourself.

Know Your Air Filter’s MERV Rating

After figuring out the size, you must determine the air filter with the right MERV rating before you can replace it. The MERV rating is a measurement of how effective the air filter is at filtering out small particle contaminates. The higher the rating, the better the filter is at maintaining good air quality and removing contaminants.

However, a higher rating isn’t always better, you’ll want to find what works best for your home and lifestyle. The higher MERV rating filters do filter more effectively, but they are thicker, and your HVAC system has to work harder to circulate the air. Consequently, this will increase your energy bills.

A MERV rating of 5 to 8 is effective for most homes. This offers enough filtration for dust mites, dander, and mold or pollen spores without taking a toll on efficiency. These filters should still be changed regularly

If you have respiratory conditions or allergies, then it’s best to get a filter with a 10 or 12 rating. These higher ratings are better at capturing allergen particles – down to one micron – such as mold spores, pollen, exhaust, and more.

If you need assistance changing your air filter or with your general HVAC maintenance or repairs, contact us at Bell Brothers!