First you need to determine the size of the image you are matting. The image size may be smaller than the paper. For example, you can print an 8x10 image on 8 1/2 x 11 paper. In this case the image size is 8x10. For an 8x10 image size there are three common mat opening sizes:
1/8 inch overlap. For this option you subtract a 1/4 inch from the size of your image. If your image is horizontal, you would select a width of 9 3/4 inches and a height of 7 3/4. This will allow the mat to overlap the image by 1/8 of an inch on all for sides. This option will prevent the edges of the image from showing, help hold it down if the paper size is also 8x10, and will mask very little of the image. If you image is portrait you would select 7 3/4 width and 9 3/4 height.
Example: 8" x 10" horizontal image, 1/8 inch overlap and 2 inch borders
- Inner Width: 9 3/4
- Inner Height: 7 3/4
- Top Border: 2 1/8
- Side Borders: 2 1/8
1/4 inch overlap. For this option you subtract 1/2 inch from the size of your image. If your image is horizontal, you would select a width of 9 1/2 inches and a height of 7 1/2. This will allow the mat to overlap the image by a 1/4 of an inch on all for sides. This option will prevent the edges of the image from showing, help hold it down if the paper size is also 8x10, and make it easier to center the image inside the mat opening. This option will cover up more of the image than the above option. If you image is portrait you would select 7 1/2 width and 9 1/2 height.
Example: 8" x 10" vertical image, 1/8 inch overlap and 2 inch borders
- Inner Width: 7 1/2
- Inner Height: 9 1/2
- Top Border: 2 1/4
- Side Borders: 2 1/4
Float mount. This option is used to show the entire image within the picture frame. Typically you select an opening that is 1/2 to 1 inch larger than the image. For instance, if you have an 8x10 image you might select an opening that is 9x11. This will leave 1/2 inch gap between the image and the edge of the mat opening. If the paper the image is printed on is larger than the image then the paper will be visible and the mat will still hold the image down. If the image is the same size as the paper, then the edge of the paper will be visible and the image mounting board will be visible.
Custom Borders
If you want your image centered, then the top, sides, and bottom borders should all be equal. Typically the frame edge will overlap the edge of the mat. For this reason it is common to add 1/8 of an inch to the borders.
Example: 8" x 12" image centered
- Inner Width: 11 3/4
- Inner Height: 7 3/4
- Top Border: 4 1/8
- Side Borders: 4 1/8
If you want to bottom weight your image then you just select a bottom border a little larger than the top and side picture frame borders.
Example: 11" x 14" horizontal image, 1 inch bottom weight
- Inner Width: 13 3/4
- Inner Height: 10 3/4
- Top Border: 3 1/8
- Side Borders: 3 1/8
Example: 11" x 14" vertical image, 1 inch bottom weight
- Inner Width: 10 3/4
- Inner Height: 13 3/4
- Top Border: 3 1/8
- Side Borders: 3 1/8