Step 9: Mount them on your foam poster board (or whatever you feel like mounting them on)
Here's how I did my measurements. I decided I wanted a .125inch gap between each picture, so I needed to figure out what the dimensions of the whole photo would be.
Since there are 3 gaps between the 4 photos, you just need to multiply .125 by 3, and add 24 (remember 4 x 6 pictues, so 6 inches times 4 pictures) to get the total length of 24.375 inches.
Do the same thing to get the height except after you multiply .125 by 3, add 16 to get 16.375.
The dimensions of the poster board are 28 x 22, so to find what the border dimensions will be, just subtract 24.375 from 28, and subtract 16.375 from 22. The dimensions of the border from the edge of the board will be 1.8125 x 2.8125 inches. Wooohooo done with math!
Before i glued the photos on the poster board, I drew the border lightly in pencil using a ruler and yard stick as a straight edge. This allowed me to easily align the photos on the outside. The pencil erased easily off the board.
My measurements kept the image pretty straight, but not perfect since I glued all of the photos by hand. If you have any other ideas on how to align the photos, feel free to try them and share.