Lets look at this another way. You may also need to account for mortar joints. Lets say the mortar between blocks is 1/2 inch. Each block, plus mortar measures 16.5 inches or 1.375 feet. Now your 17 feet becomes 12.36 blocks long (or 12 blocks with 6-inches left over); and your 7-foot length is 5.09 blocks (or 5 blocks with 1.5 inches left over.

Now, it would be easier to change the dimensions of what you are building to fit an even number of blocks, 12 x 5 (60) blocks with 1/2 mortar joints = 16.5 x 7 feet. If you cannot change the size, you are going to do a bunch of cutting and will require 2 additional blocks.

So 7-1/2 blocks will not complete the job. Figuring it your way, without accounting for mortar: 17x7 = 119 sf project, and 16x16/144 =1.7778 sf/block. So 119/1.78 = 66.85 blocks.

Hope this helps. What are you building / making?

I knew I was skipping an important step. Unfortunately I cannot change the dimensions of the bed/deck. It's an existing plant bed that a friend wants to convert to "patio" and there is concrete on one side and pool decking on the other. I was planning to use landscape cloth (or plastic to avoid weeds) and "quick-crete" so I think the mortar issue is minimal at best, yes??

Thanks again.

OK, your block estimate just went up:

17 feet / 1.3333 = 12.75 blocks

7 feet x 1/333 = 5.25 blocks The cutoffs (1/4 block) from the 17 foot direction will be used for the 1/4 block needed in the other direction, so 13 x 5 = 67 blocks (you still need 2 extras to cut in quarters). Hey, what do you know, we estimated 67 the first time! I would buy a couple extra to account for the oops factor that I almost always encounter.

Thanks for checking back.