Convert 1 inch Filter To 4 inch? (Everything You Must Know)

An air filter ensures smooth airflow in an HVAC system. This means that the filter’s capacity could affect the air quality negatively or positively.

For example, a one-inch filter can easily get clogged and reduce proper airflow. 

In contrast, a four-inch filter has adequate surface space to trap and filter contaminants to ensure better airflow, so a conversion from the former to the latter would be a wise choice. 

You can convert a one-inch filter to a four-inch filter by turning off your HVAC system, locating the filter, removing the one-inch filter, ensuring that the four-inch filter fits perfectly into the filter frame, cleaning the filter frame, covering thoroughly, and finally screwing in the four-inch filter.

How Do I Convert a One-Inch Filter to Four-Inch? 

Convert One-Inch Filter to Four-Inch

To convert a one-inch filter to a four-inch filter, you need to cut the flange of the I-inch air filter’s frame, replace it with a frame that suits a four-inch filter, and install the 4inch filter.

By converting a one-inch filter to a four-inch filter, your HVAC will enjoy unrestricted airflow due to the higher MERV rating.

An HVAC system relies partially on the proper functioning of its air filter to be effective.

As a result, proper knowledge of converting a one-inch filter to a four-inch filter is valuable and essential.

Below is a step-by-guide to aid you:

  •  It is essential to begin this process by ensuring that your HVAC system is turned off and unplugged from its power source. 
  • Next, locate the filter in your HVAC system; it could be on the wall, under the grille, in the air handler cabinet, or in a filter rack with a removable door outside. This step depends on your HVAC system, so search these locations until you locate the filter. 
  • Remove the one-inch filter by unscrewing it from its frame and the cover. Keep the screws safe for the four-inch filter installation and clean the filter frame thoroughly to remove all dirt and moisture.
  • Check if the four-inch filter fits the frame where the one-inch filter previously was. If it does not fit, you will need to purchase and install a frame that fits as it needs to fit perfectly. 
  • Now you can finally install the four-inch filter by screwing it into the filter frame of the HVAC system and turning it back on.

Can I Change My Air Filter Size? 

You can change your air filter size no matter what size your HVAC filter originally came with.

However, a larger air filter size is more effective in filtering dirt and other particles that are likely to accumulate quickly and clog the airflow of your HVAC filter. 

All you need to know to choose the best air filter size to replace an old one is a standard HVAC air filter size chart.

You can find this detailed air filter chart below; 

Displayed Filter Size Actual Filter Size 
14 x 14 x 113 3/4 x 13 3/4 x 3/4
14 x 20 x 1 13 1/2 x 19 1/2 x 3/4
14 x 24 x 1 13 3/4 x 23 3/4 x 3/4
14 x 25 x 1 13 3/4 x 24 1/2 x 3/4 
14 x 30 x 113 7/8 x 29 7/8 x 3/4
15 x 20 x 114 1/2 x 19 1/2 x 3/4
16 x 16 x 115 1/2 x 15 1/2 x 3/4
16 x 20 x 1 15 1/2 x 19 1/2 x 3/4
16 x 24 x 115 1/2 x 23 3/8 x 3/4
16 x 25 x 115 1/2 x 24 1/2 x 3/4
16 x 30 x 115 1/2 x 29 3/4 x 3/4
18 x 18 x 117 1/2 x 17 1/2 x 3/4
18 x 20 x 117 1/2 x 19 1/2 x 3/4
18 x 25 x 1 17 1/2 x 24 1/2 x 3/4
18 x 30 x 1 17 1/2 x 29 3/4 x 3/4
19.5 x 23.5 x .7519.3/8 x 23.3/8 x 3/4
20 x 20 x 119 1/2 x 19 1/2 x 3/4
20 x 24 x 1 19 1/2 x 23 1/2 x 3/4
20 x 25 x 119 1/2 x 24 1/2 x 3/4
20 x 30 x 119 5/8 x 29 5/8 x 3/4
24 x 24 x 123 3/8 x 23 3/8 x 3/4
24 x 30 x123 1/2 x 29 1/2 x 3/4
25 x 25 x 124 1/2 x 24 1/2 x 3/4

Can I Use a 2-inch Filter Instead of a 1-inch Filter? 

You can replace your one-inch filter with a 2-inch filter as long as your air filter frame can accommodate its thickness.

It is always a good idea to upgrade your air filter to a larger size to improve airflow in your home or office space.

Replacing a one-inch filter with a 2-inch filter is also relatively easy as the sizes are an inch away from each other; you can rely on the step-by-step guide above to aid you in converting your one-inch filter to a 2-inch filter. 

If the 2-inch filter you decide to go with has a higher MERV rating than your one-inch filter and your HVAC system supports it, this is even better as it boosts the overall efficiency of the HVAC system upon installation. 

What Happens If I Choose the Wrong Filter Size? 

Choosing the wrong filter size for your HVAC system does not effectively prevent dust from clogging the HVAC system.

Sometimes, the filter can get stuck in the ventilation system and dirties your HVAC system quickly. 

Finding the perfect filter for your HVAC system is of utmost importance because a smaller or bigger-sized air filter could cause complications such as; 

#1. Excess And Easy Dirt Build-up

 A smaller-sized air filter leaves space for dirt to easily slip into the air filter and accumulate quickly. This accumulation of dirt in the filter eventually clogs it and restricts proper airflow. 

#2. Inability to Filter Dirt Properly

When you use a filter with a higher MERV rating than what your HVAC system has to support, the HVAC system will have difficulty pulling enough air through the filter, damaging it. 

#3. Reduced Cooling And Heating Efficiency

 Using the wrong filter will cause a lag in your HVAC system’s cooling and heating capacity and cause problems that would cost you heavily to rectify.

Do not force a giant filter to fit into a space where it does not fit, nor should you neglect to fit a small-sized filter perfectly. 

Which Filter Size Should I Use? 

You can determine the perfect filter size for your HVAC system by determining the exact dimensions of your air filter frame before purchasing a new filter to replace the old one.

 Unfortunately, while filter sizes may be on air filters in stores and online, they are rarely the exact size as the dimensions. So you still need to measure it manually or refer to a “true to size” filter chart. 

A detailed “true to size” or standard filter chart is above to help you figure out the exact size of filters that have filter sizes that differ from their actual size.

Of course, always use a measuring tape or rule to ensure you’ve picked the right size. 

This action will save you from making returns or struggling to make the wrong size filter fit into the air filter frame. You can get your air filter’s exact size by removing it and placing it on a flat surface.

Then, use a measuring tape (inches) to measure the length, width, and depth of your previous air filter, and round it up to find the nominal size (printed or tagged price) to know which to purchase at a store or online.

No one can dictate the perfect air filter size because HVAC systems differ; if you are only looking for a new air filter to replace the old one, you can check for the size or dimensions indicated on the old one if it is still visible.

 However, if you’re looking for a new air filter that is a different size for more effective airflow, you’d need to get accurate measurements before purchasing a new one. 

Final Thoughts

To convert a one-inch filter to a four-inch filter, you primarily need to know the perfect fitting method.

Depending on the HVAC system’s specifications, you can convert your one-inch filter to a two-inch one.

Ensure that you always refer to a “true to size” chart when picking a new filter for your HVAC system.

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