Proper Mat Size for Matting an Image

Framing involves many different aspects. Determining the proper mat size and mat opening for a print or photograph is one of the more confusing issues facing novice framers.

First, be sure you understand the two different measurements associated with a frame mat. There is the overall size of the mat, which is around the size of the inside of the frame. Then, there is the mat window measurement, which refers to the size of the opening in the mat through which the image shows.

Measure the Dimensions

To determine the general overall dimensions of the mat, measure the glazing size (size of the glass or acrylic) of the intended frame. If the glass fits inside the frame without too much wiggle room, it provides a good template for cutting the mat to its overall size. There is some room for error in cutting, since part of the frame will conceal smaller irregularities, but keep in mind there is only about a 1/8” margin of error before you start noticing imperfections in the framing job.

As for the size of the window in the mat, one simple general rule is that the opening should not be the same size as the print or photo. Cutting a mat to the exact dimensions of the outer border of a picture or photograph is almost impossible and it is nearly impossible to get them lined up perfectly.

Off- the- shelf pre-cut picture frames usually have mat boards with openings 1/2 an inch smaller than the intended picture size. For example, a 16×20 inch frame including a mat purchased for use with 11×14 prints or photographs will have an actual window opening somewhere in the neighborhood of 10 1/2 x 13 ½ inches. This results in the mat overlapping each side of the print by ¼ inch. A quarter of an inch does not sound like much on its own, but consider that it adds up since there are four sides on every mat.

Matting Techniques

float mountingAlthough allowing the mat to overlap the image is the most common matting technique, sometimes employing the practice of using a mat opening that is larger than the image, known as “float mounting”, works best. This matting technique prevents any masking of any part of the framed image. It is especially useful when the ability to view the artist’s signature or print data is desired.

There are several ways to accomplish this look, including using different overlap measurements on different edges of the work. Usually the side and top border measurements are between 1/4 to 1/2 inch and the bottom is expanded to reveal between 1/4 and 1 inch of the border. In most cases, the bottom dimensions of a mat are equal to the top and sides, but the presence of a signature changes all that. However, getting it right requires a little math along with some good measuring skills. Beyond that, another common mistake is to forget to double the border size when calculating the opening.

For example, if the signature is under 1/2 inch, then you can use 1/4 or 3/8 inch top and side borders and 1/2 inch bottom border. If the signature requires 3/4 inch, then you can use 1/2 top and side borders. In this case, the mat opening will be one inch larger than the image width, and 1 1/4 inches larger than the image height.

Sometimes drawing out a sketch prior to making any cuts helps better visualize your aims. Beyond that, never forget that the adage, “measure twice, cut once” does not just apply to woodworking.

Mats are integral parts of framing. Their color accents the framed item, setting it off to its best effect. Their composition ensures preservation of the item. However, mats serve other purposes. They provide a buffer layer between the artwork or photo and the frame glazing. Beyond that, the mat board helps keep the framed image flat within the frame, and adds another way to create a truly distinctive and unique framed look.

Frame Destination carries several varieties of mats, including 100% cotton, acid-free and lignin-free mats with solid color throughout, mats that trap and neutralize pollutants and acid by-products, and paper mat featuring white or cream cores. All mats from our shop feature larger windows than most store-bought mats, meaning more of the image showing through in a framed piece. All artwork below 20” on each side has mat windows cut ¼ of an inch smaller, which allows for just 1/8 of an inch overlap for each side. Opening for images 20” and larger on both sides are cut ½” smaller. The slightly enlarged cut out window still allows for sufficient coverage or overlap of any paper border around the image, thereby supporting the image, and negating any concerns about the color of the substrate the image is mounted against showing up in the completed framed item.

About the author


Mark Rogers is an amateur photographer and the founder of Frame Destination, Inc. In 2004 Mark realized the framing industry was not keeping up with the evolution of photography via new digital technology and started Frame Destination in his garage. Now his company has thousands of do-it-yourself framing customers across the US that it helps with its 11,000 square feet production facility in Dallas, TX.

20 thoughts on “Proper Mat Size for Matting an Image”

  • Trotter Hardy

    Hi. Just noticed something. Above, you say this: "All mats from our shop feature smaller windows than most store-bought mats, meaning more of the image showing through in a framed piece."
    I think you mean either "smaller BORDERS" or "LARGER windows," not "smaller windows." Otherwise, a very helpful explanation--thanks.

  • Mark Rogers

    Thanks Trotter, you are correct the window is larger not smaller. Great catch!

  • Tina Spry

    If I have a image that is 8x8 what size frame and what size mat should I buy?

    • Mark Rogers

      Tina, I would go with a 2 inch mat border for 12x12 frame such as this basic wood frame for $30:

      If you have space on your wall you can select the next size up which is 8x8 photo size and wood frame size of 16x16 with 4 inch borders that will provide more of a gallery frame look.

  • Nancy

    If I am painting a water color to fit inside a 4 x 6 frame.
    What is the standard matt size to fit on picture? I was wondering because I want to paint the design to be just inside where matt will cover.

    • Mark Rogers

      Nancy, that would be 3x5 but you might check on the actual mat board first. The opening has to be smaller than a 3x5 photo to help hold it down so the matte opening might be 2-1/2 x 4-1/2 or 2-3/4 x 4-3/4. At such as small size that difference might be an issue for the artwork image you are framing.

  • Derrick Arnold st
    Derrick Arnold st December 5, 2017 at 3:13 pm

    I have a 6X20 picture what size mat and picture frame is needed.

    • Mark Rogers

      Derrick, I would use a mat with borders just over 2 inches at 2-1/8 inches
      Artwork Size: 6" x 20"
      Mat Window Opening: 5 3/4" x 19 3/4"
      Picture Frame Inside: 10" x 24"
      Picture Frame Outside: 11 1/8" x 25 1/8"

      Here is an example of a basic black wood picture frame with a white mat that would fit your 6x20 picture:

      You can easily change the mat color and frame on that page. You can also select a more archival mat like the Alphamat.

  • Kim

    I have a 16 x 20 picture to frame what size mat and what size frame do you suggest? I’m not sure and you seem pro at this!

    • Mark Rogers

      Hi Kim, that is pretty large print so if you have the wall space I would do 4 inch borders. The mat will overlap the photo a little so mat window of 15 3/4" x 19 3/4, borders of 4-1/8 inches and a picture frame size of 24x28 inches.

  • Linda Sorsby

    Could you suggest the best size mat to use for a print that is 29 X 39 with a sight size of 21.5 X 29.5? Thank you!

  • Mark Rogers

    Hi Linda, assuming your print is 29 wide and 39 tall and you do not want to cut the print then I would suggest you make the side mat borders 4 inches and the top and bottom 5 inches. For a print that size I suggest you overlap the photo by 1/4 inch all 4 sides.
    Artwork Size: 21 1/2" x 29 1/2"
    Mat Window Opening: 21" x 29"
    Mat Outside: 29" x 39"

    With a print paper of 29 x 39 if you get a picture frame that is 29x39 then you do not need to mount it since they are the same size.

  • Jenn

    HI there!

    If I have a 12x18 poster- what size matting should I use and then what size frame?



    • Mark Rogers

      Jean you can use 3 inch mat borders for a picture frame that is not too large. The frame size ends up being 18x24 if you use mat borders that are 3-1/8 inches.

      Artwork Size: 12" x 18"
      Mat Window Opening: 11 3/4" x 17 3/4"
      Frame Inside: 18" x 24"

      Here is an example of a black frame from us that size for less than $50

  • Ranae

    Need your advice to order two mats as I haven't done this before. Frame interior (glass size) 21 15/16" high x 18" wide and the print going in the frame is 16" high x 12" wide. Can you advise on the size to order?

    The second one I want to keep in a particular frame that is 16" high x 20" wide but the drawing has different visual space on top vs. the sides. The top has 2" of white space to the edge of the drawing, the bottom has 1 1/2" space to the signature line, and the sides have 1" space until drawing begins. What size of mat should I do?! Thank you for your help!

    • Mark Rogers

      Hi Ranae, assuming you would like the mat to overlap the print by 1/8" on all 4 sides the first one would be:

      Artwork Size: 12" x 16"
      Mat Window Opening: 11 3/4" x 15 3/4"
      Mat Outside: 18" x 21 15/16"
      Side borders: 3-1/8"
      Top/Bot borders 3-3/32"

      On the 2nd one you might make the window opening 1/2 inch larger than the image on the top and sides to show some of the border. The bottom you make just large enough to show the signature. The other option is to cover the paper and borders. For that you would just make the window opening 1/4 inch smaller than the image size (not the paper size). To give you more info I would need the image size and the measurement from the bottom edge of the image to the bottom of the signature.

  • Debbie Blecha

    Hello!!! I have a print that is 24 x 17.......and I would like the matting and frame to be something like 48 x 34 is this possible?

    • Mark Rogers

      Sure that is possible Debbie! Most frame materials are made up to 32x40 so when you get above that size the selection goes down and the price goes up, especially the shipping cost. It still might be much less expensive to get it from an online company like ours then to have a custom frame shop do it for you. In our case you just select a frame and then customize the size. Enter artwork of 24x17 and I suggest you change the overlap of the mat from 1/8 inch to 1/4 inch. Enter the picture frame size of 48x34 and the site will calculate the borders which will be pretty large at around 8 and 12 inches. Large mat borders like that give the picture frame a very strong gallery look and feel. It also really separates the artwork from the rest of the room. Be careful not to pick a top mat color that will distract from the art though. Here is an example I through together on our site. If you need the frame to be more archival you will want to change the mat and backing to acid-free and perhaps the acrylic to UV-filter. Also, it is more common even for custom frame shops to go with acrylic when the frame is over 32x40 since glass is so heavy.
      Wood picture frame example

  • Craig

    How big of a mat should I use for framing a newpaper? The newspaper is 11" x 21"?

    • Mark Rogers

      Craig, I assume this newspaper print is something memorable and you want to keep it for a while so I suggest a picture frame with archival framing with UV glass and acid free mat and mounting board. Because it is a long frame, you might like the mat side borders being a little smaller than top and bottom. I suggest 2-5/8 for side mat borders and 3-1/8 inch for the top and bottom mat borders. I suggest you have the mat overlap the newspaper 1/4 inch on each side the window would be 10-1/2 by 20-1/2. I also suggested a photo white mat which is not as bright as normal white mat.

      Here is an example complete picture frame with a simple brown wood profile:

      Artwork Size: 11" x 21"
      Mat Window Opening: 10 1/2" x 20 1/2"
      Frame Inside: 16" x 27"


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