**AC and furnace air filters** come in a variety of different sizes and types. If your *air filter size* is not available at your local *Home Depot*, *Lowe’s*, or *ACE Hardware,* then buy them online and save some money while doing so.

### Best way to purchase & save money on home furnace air filters

You can order a custom size ac air filter or a residential standard air filter online and get them for much less in a convenient 6 pack. Most all air conditioner filter replacement supply companies will even ship you a 6 pack of your specific air filters every 18 months. This is a handy way to always have the correct size and type on hand. You will also remember to change your air filter on a regular basis since they are being delivered to your home.

Here are some printable coupons and rebates for ac air filters for the ** 3M brand Filtrete**.

### Choosing the correct air conditioner air filter size

Most **air conditioning filters**, **furnace filters**, and **HVAC filters** are the same exact thing. You will find that **HVAC technicians will usually refer to your filter as an “air filter” in the summer and as a “furnace filter” in the winter**. A key thing to know about your air filter when ordering a replacement is the correct size. You will need to know the length, the width, and also the thickness (depth) when ordering a replacement. Most filters will have the dimensions printed on the side. If there are no sizes printed on your filter, measure your air filter with a tape measure to find the dimensions… And if you were wondering, the numbers are interchangeable. Here is an example: 20″ x 25″ x 1″ is the same as 25″ x 20″ x 1″. Common filter sizing is referred to like this:

*LxWxD*or

**length x width x depth**or height.

**When ordering filters online, make sure you are ordering the correct depth air filters**. This is a common mistake as many people get the first 2 numbers correct (length and width) but forget or ignore the last number which is the depth or thickness.

### Choosing what type of AC or furnace air filter is best

Once you have the dimensions you will need to choose the level of air filtration by choosing what type of air filter suits you best. There are different types of air filters for different types of environments. Some filters are designed for maximum energy efficiency while others remove more particles from the air. **If you have pets or smoke in your home, you should replace your air filter more often.** You should also upgrade your filter to one that has a higher *MERV rating* for maximum air filtration.

### Quality and effectiveness of ac air filters

In the air filter world, there are cheap air filters and there are expensive air filters. The effectiveness of an air filter is measured in **MERV ratings** *(Minimum Efficiency Reporting Value)*. This rating system breaks the filters down into specific categories. **The higher the MERV number or category, the better the air filtration.** Filtration performance is determined by the size and density of the material it’s made with as well as the size and volume of the air particles that are being filtered. The more dense the filter is, the more difficult it is for the air to pass through. This can result in higher energy usage and reduces efficiency. A less dense cheaper air filter will let the air flow through more efficiently but will not catch as many particles in the air. Those are a few of the differences in the types of filters available today. Your air filtration choice should depend on your current living situation such as if you have pets, you smoke, or you have allergies.

### Home air filters and the air quality inside your house

The air pollution in your home is among the top 5 environmental health risks. You can make the air quality in your home exceptionally better by simply changing or **upgrading your air filter**. One brand that has the highest quality home air filters is the **3M brand** called ** Filtrete**. The type of air filter you will need factors on the amount of particles in the air and the people in your home that may have allergies. If you have a smoker in your home you should upgrade it to a higher MERV rating and change it at least every month.

### How often to replace air conditioner filters

To ensure the efficiency of your air conditioner you should replace air filters routinely. **Change your AC filters every 30 days** is best for optimal performance of your air conditioner. **For a furnace it is recommended to change the filter out every 4 or 6 weeks** in the winter time. *What happens if my air filter is clogged?* A clogged air filter will block the needed airflow and make it impossible for the AC to run efficiently. When the air that flows through the filter is obstructed, that air can slip around and behind the filter bringing in all kinds of dirt and dust to the evaporator coil. When this happens the heat absorbing capacity of the coil is reduced significantly. **By removing and replacing a dusty obstructed air filter with a new one, you will reduce the amount of energy it takes to run your AC by 4% to 17%.**

**Standard and hard to find 1″ Air Conditioner Air Filters (Sizes)**

*Click here to find your 1″ replacement air filter size online*

**10 x 10 x 1″** (usually not found in stores)

10 x 14 x 1″

**10 x 30 x 1″** (usually not found in stores)

12 x 12 x 1″

12 x 20 x 1″

12 x 24 x 1″

**12 x 30 x 1″** (usually not found in stores)

14 x 14 x 1″

14 x 20 x 1″

**14 x 24 x 1″** (common)

14 x 25 x 1″

14 x 30 x 1″

16 x 16 x 1″

16 x 20 x 1″

16 x 24 x 1″

**16 x 25 x 1″** (common)

18 x 18 x 1″

18 x 20 x 1″

18 x 24 x 1″

18 x 30 x 1″

**20 x 20 x 1″** (common)

20 x 22 x 1″

20 x 24 x 1″

**20 x 25 x 1″** (common)

20 x 30 x 1″

24 x 24 x 1″

24 x 30 x 1″

25 x 25 x 1″

30 x 60 x 1″

**Standard and hard to find 2″ Home Air Filters (Sizes)**

*Click here to find your 2″ replacement air filter size online
*8 x 16 x 2″

8 x 30 x 2″

10 x 10 x 2″

10 x 15 x 2″

10 x 16 x 2″

10 x 20 x 2″

10 x 24 x 2″

10 x 25 x 2″

12 x 12 x 2″

12 x 16 x 2″

12 x 18 x 2″

12 x 20 x 2″

12 x 24 x 2″

12 x 25 x 2″

12 x 27 x 2″

12 x 30 x 2″

12 x 36 x 2″

14 x 14 x 2″

14 x 18 x 2″

14 x 20 x 2″

14 x 24 x 2″

14 x 25 x 2″

14 x 30 x 2″

14 x 36 x 2″

15 x 20 x 2″

15 x 25 x 2″

15 x 30 x 2″

16 x 16 x 2″

16 x 20 x 2″

16 x 24 x 2″

16 x 25 x 2″

16 x 30 x 2″

16 x 36 x 2″

17 x 20 x 2″

17 x 22 x 2″

17 x 25 x 2″

18 x 18 x 2″

18 x 20 x 2″

18 x 22 x 2″

18 x 24 x 2″

18 x 25 x 2″

18 x 30 x 2″

18 x 36 x 2″

19 x 21 x 2″

20 x 20 x 2″

20 x 22 x 2″

20 x 23 x 2″

20 x 24 x 2″

20 x 25 x 2″

20 x 30 x 2″

20 x 36 x 2″

21 x 22 x 2″

22 x 22 x 2″

22 x 24 x 2″

24 x 24 x 2″

24 x 30 x 2″

24 x 36 x 2″

25 x 25 x 2″

25 x 28 x 2″

25 x 29 x 2″

25 x 32 x 2″

27 x 27 x 2″

28 x 30 x 2″

29 x 29 x 2″

30 x 30 x 2″

**Standard and hard to find 4″ AC Air Filters (Sizes)**

*Click here to find your 4″ replacement air filter size online
*8 x 16 x 4″

8 x 30 x 4″

10 x 10 x 4″

10 x 15 x 4″

10 x 16 x 4″

10 x 20 x 4″

10 x 24 x 4″

10 x 25 x 4″

12 x 12 x 4″

12 x 16 x 4″

12 x 18 x 4″

12 x 20 x 4″

12 x 24 x 4″

12 x 25 x 4″

12 x 27 x 4″

12 x 30 x 4″

12 x 36 x 4″

14 x 14 x 4″

14 x 18 x 4″

14 x 20 x 4″

14 x 24 x 4″

14 x 25 x 4″

14 x 30 x 4″

14 x 36 x 4″

15 x 20 x 4″

15 x 25 x 4″

15 x 30 x 4″

16 x 16 x 4″

16 x 20 x 4″

16 x 24 x 4″

16 x 25 x 4″

16 x 30 x 4″

16 x 36 x 4″

17 x 20 x 4″

17 x 22 x 4″

17 x 25 x 4″

18 x 18 x 4″

18 x 20 x 4″

18 x 22 x 4″

18 x 24 x 4″

18 x 25 x 4″

18 x 30 x 4″

18 x 36 x 4″

19 x 21 x 4″

20 x 20 x 4″

20 x 22 x 4″

20 x 23 x 4″

20 x 24 x 4″

20 x 25 x 4″

20 x 30 x 4″

20 x 36 x 4″

21 x 22 x 4″

22 x 22 x 4″

22 x 24 x 4″

24 x 24 x 4″

24 x 30 x 4″

24 x 36 x 4″

25 x 25 x 4″

25 x 28 x 4″

25 x 29 x 4″

25 x 32 x 4″

27 x 27 x 4″

28 x 30 x 4″

29 x 29 x 4″

30 x 30 x 4″

**Standard and hard to find 6″ ac Air Filters (Sizes)**

*Click here to find your 6″ replacement air filter size online
*12 x 24 x 6″

16 x 20 x 6″

16 x 25 x 6″

18 x 24 x 6″

20 x 20 x 6″

20 x 24 x 6″

20 x 25 x 6″

24 x 24 x 6″

MERV ratings for your home air filter replacement

*Do you have an air filter question? Leave a comment below and we will answer you back in a timely manner.*

claraI was looking to buy AC Filters online.

I was looking for a guide to help me out. I stumbled upon your blog and I found what I needed.

TeddyHow do I know for sure if I need an air filter that is thicker than 1 inch? Our house had a 1 inch thick filter when we bought it, but it has to be weighted down in the handler under the unit in the garage.

Levi AllenI’m not trying to convert what’s on the handler.

I just want to remove the filter and cap it off.

And in the wall near the air handler, where the current inlets are located, to install framing to add filters at that location.

DIY Project Help TipsLevi,

We are not aware of a kit to convert the air inlet grill from 1″ to 4″.

Are you simply trying to get more air filtration?

What is the purpose of converting the air inlet?

-RR

LeviI have a question about converting the 1″ central air filter that goes inside the unit, to a 4″ Merv 11+ that can go where the air inlet grill in the wall is located.. Is there a kit somewhere, or is this something I need to build myself?

DIY Project Help TipsCindy Roberts,

If the AC filter is 10x20x1, then using ultra cheap filters that are the wrong size and doubling them up is not efficient.

They are just being cheap or possibly they ran out of the correct size air filters and this is just a one time thing.

You need to tell them you want the correct size and thickness AC air filter.

10x20x1 is what needs to be installed.

If apartment maintenance is putting a 10x10x1 and another 10x10x1 air filter then this is wrong and is inefficient.

You need to call the apartment management and tell them this is not the proper way to replace AC air filters.

Here is a 12 pack of medium quality 10x20x1 air filters…. They cost about $19 US dollars.

-RR

Cindy RobertsI just moved from a home where I purchased my air filters from Ace Hardware, all of the homes in the area were built by the same builder, thus all had the same AC unit needing the same size air filter. The local grocery store also carried the same size for around $5.00, but as soon as they were delivered, they sold out. I was surprised finding such a variety of kinds at Ace. The manager asked if I needed help, I knew the size and thickness, and she started going down the list. Do you have pets, allergies, do you live on the golf course, very generic questions, but she basically told me the filter I should be buying, for the atmosphere in my home.

It was a lot more than $5.00, but it helped a lot with my allergies, and I wasn’t needing to dust as often. I still had to change it monthly, but it made the air feel “clean” so it was worth every penny, and it saved me just about the same amount of money on my AC bill, a great feature in Arizona, where your AC runs 8-9 months each year.

I now live in an apartment, and if you call maintenance they supply and install new cheap air filters each month. The measurement would normally be 10x20x1 what is best, there’s of course is 1 (inch).

However, what they install is 10x10x1, and one next to it 10x10x1? Am I still getting the efficiency I need? In the center where they meet is cardboard to cardboard, wouldn’t that affect absorption and air distribution? What say you, the experts?

DIY Project Help TipsThomas,

The best AC air filter if you are sensitive to animals and have allergies or even asthma, the 3M Filtrete 1500 Ultra Filter is probably your best bet.

This 3M Filtrete Allergen Reduction Filter has improved filter efficiency through electrostatically charged fibers. They claim 90% effective at capturing large allergens like mold and pet dander and 25% more efficient compared to Filtrete Micro Allergen Filters.

-RR

ThomasI have severe allergies and 4 cats. I know what size of air filter for home ac i need. Can you tell me which air filter for my home air conditioner will be the best for filtering out hair and dander from pets? Also which last longest?