i am trying to calculate how many half square triangles to put on a 30" square border. i am totaling confused. can someone help?

If you're going to make HST blocks, then I would find what size finished block goes into 30. So say your finished size is 2" then on the sides it would equal 15 blocks each and on the top and bottom you would add 2 blocks for a total of 17 for those.

You would want your unfinished block size to be 2 1/2". Did I confuse you more?

Depends on the look you are after - each side could have (30)one inch, (15)two inch, or (5) three inch. Graph paper will let you see which you like better.

interesting thread, thanks

I love using graph paper, its the only way I can figure stuff out.