Since I am a self-proclaimed math nerd, there's no point in denying it, I have a math degree. Nerd alert! I thought I would share my number crunching fun with you. Doesn't everyone love math? Well, let this mathie help you out with planning your molding install.
Step 1 - Measure your wall. Mine is 168" long x 96" high (8 foot ceilings)
Step 2 - Determine the height of your chair rail (from the floor). For 8 foot ceilings about 36" is standard, for 9 foot ceilings you could do 42" (to the TOP of the chair rail). If you have a table picked out, you'll want the chair rail to be a couple of inches higher than the table. My table is 32" high so the BOTTOM of the chair rail will be set at 36".
Step 3 - Determine the height of your baseboard. If you are not replacing it, just measure, otherwise pick your new baseboard. Mine is 4.75"
Step 4 - Determine your spacing between boxes. 3" is standard, but I like a little more space in the front hall, I'm going to use 4" since my baseboard is tall, I can go a bit bigger. (you could do anything from 2" - 5" but don't go larger than the height of your baseboard or it will look out of proportion).
Step 5 - Determine the height of available wall under the chair rail. Simple math... here we go.
Distance to bottom of chair rail (Step 2) minus baseboard height (Step 3) = 36"-4.75" = 31.25" this is the amount of wall space that you have.
Step 6 - Determine the height of your boxes. Now you'll have spaces at the top and the bottom equal to Step 4 which is 4" x 2 = 8" total. So the box height is Step 5 minus 8" which is 31.25" - 8" = 23.25"
Whew! Are you still with me? We're almost there. Now we need to determine how long to make the boxes.
Step 7 - Determine how many boxes you want. This may be based on how large you want the boxes... do you want them to be tall or wide or square. I like the look of an odd number better so I'm going with 5 boxes.
Step 8 - Determine size of boxes. Total wall length (Step 1) minus spacers (Step 4 x Step 7) divided by number of boxes (Step 7) which is (168" - 4" x 5 boxes) / 5 boxes = 29.6"
If you don't like the size of the boxes you end up with you can change the number of boxes and recalculate or use varying widths for the boxes... some skinny, some wider in a pattern that you like.
We put up painters tape on the wall to mark out some of the boxes to make sure that we liked the look before we went out and bought all the molding. I'd recommend at least drawing it out on paper before you start cutting, but that's just me, I'm a planner.
If you didn't follow that at all and need help or you have questions send me an email... I'd be happy to help.