For an explanation of the Golden Ratio and how it can be applied to your picture framing design, visit the Golden Ratio Page.
Using the calculator below, if you input the height and width of your picture, it will tell you how wide to make your mount border, so that the area of the picture is in the Golden Ratio with the area of the window mount, behind which the picture is displayed.
When framing your picture note that these dimensions are the viewing size, therefore, add the width of the frame lip to calculate the glass size.

For an image to look properly balanced, behind a window mount, it is often considered necessary to correct an optical illusion that makes the bottom border seem narrower than the top, when positioned at the geometric centre. A solution to this problem is Optical Centring. The Optical Centre is a position slightly higher than the geometric centre. Therefore the bottom border is given a greater width. This is known as Bottom Weighting. A standard equation to calculate the adjustment necessary is to make the bottom border wider than the top in the ratio of 11:9 (55% to 45%).

The dimensions displayed below indicate the border widths that can provide Optical Centring (in the ratio of 11:9), while still being in the Golden Ratio with the image.

Bottom Weighting the mount border may not be accurately represented in the Golden Ratio visualisation Graphic below.