This is a common question we receive at American Frame. Many of our customers are new to DIY picture framing and border sizing is one of the variables in the framing process.
Border sizing has no set rules as to the size the borders should be in relation to the size of the window opening or frame size. It has more to do with aesthetics and economics.
Aesthetics: If the borders of the mat are too narrow or too wide, the appearance of the framed art may be adversely affected.
Economics: The larger the mat borders, the larger the mat and frame will be. This will add to the overall cost of the project.
The default border is set on our website at 2” on all 4 sides but this can be adjusted in the design process.
Many framers have a “rule of thumb” they use when suggesting border sizes to their clients. A little math is involved. Here is how it works:
Add the length and width of the mat window opening together. This number is the United Inches (UI)* of the opening. Use the following chart as a guide to determine a possible border size:
Window United Inches Suggested Mat Border
8” to 11” 1”
12” to 17” 1 ½”
18” to 24” 1 ¾”
25” to 36” 2”
37” to 44” 2 ½”
45” to 56” 3”
56” to 60” 3 ½”
Remember, these are just suggested border sizes. As DIY framer, you are free to experiment and determine what is best for your project.
When you are trying to determine your mat border size, remember that the lip of most frames will cover ¼” of your mat on each side of the frame. You may want to consider adding ¼” to the selected mat border size to account for this.
*United Inches (UI) is a common measurement used in the framing industry for determining cost of frames, mats, glazing, etc.