Unlocking the Mystery: What Are the Most Common Furnace Filter Sizes?

Winter is just around the corner, which means it's time to start thinking about your furnace. One of the easiest and most important things you can do to keep your furnace running efficiently is to regularly replace its air filter. But with so many sizes available, it can be a challenge to find the right one. If you're wondering what the most common furnace filter sizes are, you're in the right place.

The first step in finding the right filter for your furnace is to know what size you need. The good news is that furnace filters come in a wide variety of sizes, so there's a good chance you'll be able to find the right one for your system. However, it's important to note that not all filters are created equal – some are designed to catch different types of particles, and some are more efficient than others.

So, what are the most common furnace filter sizes? We've done the research so you don't have to. In this article, we'll break down the top filter sizes and provide some helpful tips for choosing the right one for your furnace. From 16x25x1 to 20x30x1 and beyond, we'll cover it all.

Understanding Furnace Filter Sizes

When it comes to selecting a furnace filter, understanding the filter size is critical. Furnace filters come in different sizes, and finding the right size can be a challenge. Here's what you need to know about furnace filter sizes:

Measuring the Filter Size: The first step in finding the right furnace filter size is to measure the existing filter. The size of the filter is usually printed on the frame, but if it's not, you can measure the width, height, and depth of the filter.

The Nominal and Actual Size: Furnace filters come in two sizes, nominal and actual. The nominal size is the size listed on the packaging, and it is typically rounded up to the nearest inch. The actual size is the exact size of the filter, and it may be up to 1/2 inch smaller than the nominal size.

The Importance of the Right Size: Using the right size of furnace filter is critical to the efficiency of your HVAC system. A filter that is too small won't provide adequate filtration, allowing dust and other particles to circulate in the air. A filter that is too big may not fit properly, allowing air to bypass the filter altogether.

Consult Your HVAC Technician: If you're uncertain about the right size for your furnace filter or you're experiencing issues with your HVAC system, consult a licensed HVAC technician. They can advise you on the right size filter for your system and diagnose any issues with your HVAC system.

Take the time to understand furnace filter sizes, and you'll enjoy improved air quality and HVAC system efficiency.

Top 5 Most Common Furnace Filter Sizes

When it comes to choosing a furnace filter, size matters. The right size ensures maximum efficiency in filtering air and keeping your home comfortable. But with so many options available, it can be overwhelming to determine which size you need. Here are the top 5 most common furnace filter sizes to help you out:

1. 16x25x1: This size is the most common and fits most standard filter cabinets. It’s perfect for smaller homes and apartments and is usually rated MERV 8 to 13 to capture even the smallest particles.

2. 20x20x1: Similar to the 16x25x1, this size also fits most standard filter cabinets. It’s ideal for homes with limited space for HVAC systems and can also be rated MERV 8 to 13.

3. 20x25x1: This size is popular in larger homes and also fits most standard filter cabinets. It’s usually rated MERV 8 to 13 and can accommodate higher air flow rates.

4. 14x20x1: Although not as common as the previous sizes, the 14x20x1 is still popular in homes with limited space for HVAC systems. It’s rated MERV 8 to 13 and can effectively capture allergens and other airborne particles.

5. 16x20x1: Another size that’s popular in smaller homes and apartments. It fits most standard filter cabinets and is rated MERV 8 to 13.

No matter what furnace filter size you need, it’s important to replace it regularly to maintain air quality and keep your HVAC system running efficiently. Consult with a professional if you have any doubts about the right size and filter type for your home.

Choosing the Right Filter for Your Furnace

Now that you know the most common furnace filter sizes, it's time to choose the right filter for your furnace. Here are some factors to consider:

1. MERV Rating: The Minimum Efficiency Reporting Value (MERV) determines how effective the filter is at trapping airborne particles. The higher the MERV rating, the better the filter's efficiency. However, a higher MERV rating can also reduce airflow, which can cause problems for your furnace.

2. Allergies: If you or anyone in your household suffers from allergies, asthma, or any respiratory condition, consider using filters with a high MERV rating for better air quality.

3. Pets: Houses with pets tend to have more pet dander and hair circulating in the air. Consider filters with a high MERV rating to trap these particles effectively.

4. Price: Filters with higher MERV ratings tend to be more expensive. Consider your budget when choosing a filter for your furnace.

5. Climate: If you live in an area with high dust or pollen levels, consider using a filter with a higher MERV rating to trap these particles.

It's important to remember to change your furnace filter regularly. A dirty filter can clog your furnace, cause it to work harder, and reduce its lifespan. Most filters need to be changed every 30 to 90 days, depending on usage and level of air pollution.

By choosing the right filter for your furnace and changing it regularly, you can improve your indoor air quality, reduce your energy bills, and prolong the lifespan of your furnace.

Maintaining Your Furnace Filter for Efficiency

Now that you know the most common furnace filter sizes, it's important to understand how to properly maintain your filter to ensure the highest level of efficiency for your heating system. Here are some tips to help you get started:

Change your filter regularly: It's recommended to change your furnace filter every 1-3 months, depending on factors such as the number of occupants in your home, pets, and overall air quality. A dirty, clogged filter can cause your furnace to work harder, leading to higher energy bills and potentially costly repairs.

Inspect your filter monthly: Make it a habit to check your filter every month to see if it needs to be replaced. If the filter appears dirty and clogged, replace it immediately. A clean filter means your furnace can run more efficiently, which will save you money in the long run.

Invest in a high-quality filter: Not all furnace filters are created equal. It's worth investing in a high-quality filter that offers superior filtration and can catch even the smallest particles. Look for filters with a MERV rating of at least 8 for the best results.

Consider upgrading to a smart thermostat: A smart thermostat can help you monitor and control your home's temperature more efficiently. It can also remind you when it's time to change your furnace filter, so you never forget.

Schedule regular maintenance: Lastly, it's a good idea to schedule regular maintenance for your heating system. A certified HVAC technician can inspect your furnace, clean and replace the filter, and address any other issues before they become major problems.

By following these tips, you can maintain your furnace filter for maximum efficiency and prolong the life of your heating system. Don't neglect this important aspect of HVAC maintenance – your wallet and your comfort will thank you.

Upgrading Your Furnace Filter for Improved Air Quality

Upgrading and replacing your furnace filter is a simple yet effective way to improve the quality of air in your home. Depending on the filter size, there are several options available to choose from that can offer improved filtration and overall better air quality.

First, consider upgrading from a fiberglass filter to a pleated filter. Pleated filters have more surface area, allowing them to capture and trap more airborne contaminants such as dust, pollen, and pet dander.

If you suffer from allergies or asthma, you may want to consider a high-efficiency particulate air (HEPA) filter. These filters are designed to capture even the smallest airborne particles and can greatly improve indoor air quality for those with respiratory issues.

Another option is to invest in an electrostatic filter. These filters use static electricity to attract and trap airborne particles, resulting in cleaner air circulation throughout your home.

When selecting a new filter, be sure to check the MERV (Minimum Efficiency Reporting Value) rating. The higher the MERV rating, the more efficient the filter is at capturing and trapping airborne particles.

Overall, upgrading your furnace filter can greatly improve indoor air quality and provide a healthier living environment for you and your family. Consult with a professional if you are unsure which filter size or option is best for your specific furnace model.


In conclusion, furnace filters are crucial components of HVAC systems, and choosing the right size for your furnace is essential to ensure optimum performance and hassle-free operation. As we have discussed in this article, the most common furnace filter sizes are 16x25x1, 20x25x1, and 16x20x1, but it's always best to check your furnace's manual or consult with a trusted HVAC technician to determine the correct size for your specific system.

Remember, regularly replacing your furnace filter is critical for maintaining the air quality in your home and prolonging the life of your HVAC system, so don't skip this crucial step!

By understanding the various filter sizes and knowing which one is right for you, you can improve the performance and longevity of your furnace, ensuring it runs optimally for years to come.

Frequently Asked Question

It's important to know the size and type of furnace filter you need before replacing it. This is because different furnaces require different sizes of filters. Your brand of furnace may need an electrostatic or media filter of a particular size - so make sure to check your old filter for these details.

Replacing your filter regularly can save you money in the long run. It helps your HVAC system become more efficient, and also keeps the air quality high. So, what are the most common furnace filter sizes?

The most popular furnace filters come in the following dimensions: 10x20, 14x20, 16x24, 18x30, 12x12, 14x24, 16x25, 20x20, 12x20, 14x25, 18x18, 20x24, 12x24, 14x30, 18x20, 20x25, 12x30, 15x20, 18x24, 20x30, 12x36, 16x20, 18x25, 24x24 and 25x25. You can use your existing filter as a reference guide to find the perfect size for your furnace. The filter dimensions should be printed on its frame as length x width x height.

In conclusion, it's important to know your furnace filter size before you replace it. Doing so will improve your HVAC system's efficiency and save you money in the long run. Plus, a clean filter is key to keeping your air quality high.

When it comes to furnace filters, exact size matters. If you get a filter that is too small or too big, air will flow around it instead of through it, meaning not all of the air will be filtered. That's why it's essential to use the right size filter for your HVAC unit.

Here's what you need to know: the size of the air filter is typically listed in the big, bold font on the packaging, which is known as the nominal size. This is a rounded-up whole-number version of the actual size, which is written in the fine print on the filter's frame. That's usually 0.25'-0.5' smaller than the nominal size, and the actual measurements of the filter may vary slightly depending on the brand.

In some cases, less common sizes come true to size, meaning the nominal size is the same as the actual size. When that's the case, it's usually noted with “actual size” in parentheses on the filter's frame.

So, the verdict is in: the answer to the question 'Do furnace filters have to be exact size?' is a resounding yes! Be sure to get the right size air filter for your system to ensure it runs smoothly and that you reap all the benefits your filter has to offer.

Are you looking for the best furnace filter? Look no further! Our team of experts at This Old House Reviews have researched the top five furnace filters on Amazon to help you find the perfect one for your HVAC system. Plus, these products are available at local home centers or online retailers like Amazon.

A great furnace filter can make all the difference. It will keep your HVAC system running smoothly, potentially leading to lower electricity bills and better air quality. That's why we've taken the time to compile a list of the best furnace filters for you.

At the top of our list is the Filtrete furnace air filter. It promises to last up to three months and outperform filters made with fiberglass. Plus, it can capture 64% of airborne particles like pet dander and pollen. This filter also comes with instructions for easy installation on HVAC systems that require filters 20 by 25 by 1 inches in size.

Customers love this furnace filter. They find it easy to install, sturdy, and a great value. However, some customers have faced difficulties with Filtrete’s app.

When choosing a furnace filter, make sure to take into account its size, filtration level, and material. That way, you can get the best filter for your specific needs.

Changing or replacing your furnace filter is one of the best ways to maintain a healthy, efficient HVAC system. But you need to make sure that you're using the right filter for your system. Here's a step-by-step guide to help you pick the perfect one!

First, measure the dimensions of your existing filter. This will tell you the length, width, and depth you need. The easiest way to do this is to look at the existing filter and buy the same size.

Next, you need to choose the right MERV rating. The MERV scale ranges from 1-20 and measures the filter's effectiveness at catching particles in the air. The higher the value, the more effective the filter is at trapping particles, but it also means less airflow.

Now it's time to decide on the type of filter. There are many options available, so take some time to research the best type for your system.

Once you have everything you need, it's time to install the filter in your furnace/air handler slot. Remove the old filter to make room for the new one.

Finally, make sure to replace your filter regularly. If it clogs up with dust and particulate, it can reduce airflow and become ineffective.

Furnace air filters are essential for your heating system. You should replace your filter at least once every three months. So, how do you select the best furnace filter for your needs? Let us help you out!

Generally, furnace filters are made up of a cardboard frame, fiberglass filter, and metal mesh. These materials work together to strengthen the filter and protect your HVAC components from dust and debris. Plus, they also help improve the air quality in your home. Without a filter, your HVAC system could become dirty and its performance would suffer.

As air passes through the furnace filter, it traps and catches any contaminants. If you don't replace or clean your filter regularly, it can obstruct airflow and cause damage to your HVAC system. In most cases, you should change your furnace filters every three months. However, you may want to replace them more or less often depending on the situation.