Get the right proportion scale for your painting easily. Enter in the original size of your painting in the first two fields. Then enter in one field in the resized field (width or height). Click "resize" to see what the other value would be if the painting was scaled proportionally.
The human eye has a horizontal field of vision of 135 degrees and a vertical field of vision of just over 180 degrees. This affects the best viewing angle and, therefore, the minimum viewing distance at which a painting of a certain size can be seen as an artwork instead of "in details."
To calculate the optimum viewing distance range which fits the human eye's ideal viewing angle:
This formula applies to prints, paintings, screens and so on...
For example, an image that is 20 by 30 inch (50 by 75 cm) has a Diagonal of 36 inches (90 cm).