Things You'll Need
Instructions
Cut your mat board down to a standard size that is larger than the size of your photo. For instance, you might cut your mat to be 8 inches wide by 10 inches high; this will make it easier for framing since frames in that size are readily available.
Turn your mat over so it sits on a table with the back side facing up toward you. Position something underneath it, such as a cutting board, to protect your table.
Measure your photograph and subtract 1/2 inch from each side. This will allow you to have your mat overlap the photograph by 1/4 inch on all four sides. Now subtract the length and width you have come up with in this step from the length and width of your mat. For instance, if your photo is 5 inches by 7 inches, this step would give you 4.5 by 6.5 inches. Eight minus 4.5 is 3.5; Ten minus 6.5 is also 3.5. Divide each of these measurements in half; now you have 1.75. The border of your mat will be 1.75 inches all the way around.
Measure a 1.75-inch border on the back of the mat and draw lines to mark it. Make sure you mark on the back of the mat board, not the front. Use your X-Acto knife or sharp cutting tool to cut the center section out of your mat.
Use tape to attach the photo to a backing board; this could be a piece of cardboard in the same size as the original mat or it could be a piece that comes with your frame. Center your photo on the backing board and then tape it down and position the mat in front of the photo when you frame it.