I have a center for round robin i want to put on point. The center is 21.5 square and i need to know what size square to cut in half for each side. Thanks

let's see -- you will want to cut half square triangles so the outer sides will be straight -- not on the bias. Measure the side of your square.

The distance across the half square triangle will be that distance plus a little to allow for wiggle room and squareing up. As an example, -- if you needed an 8 " diagonal -- the original square is 6". To make sure, you might like to make a paper "half square triangle" to exact size and use it as a pattern. Newspapers are great for this.

I hope this is helpful.
Mim

21" FINISHED divided by 1.414 = 14.85" + .5" seam allowance.

Rounded up to 15.5" CUT size.

But I'd cut them bigger (16.5+) to have the center float - gives you more wiggle room.

Double check it the other way to find the diagonal of a square:
15.5" square - .5" seam allowance = 15" FINISHED x 1.414 = 21.21"

Close enough. ;-)

wow, you're the math wiz here

:thumbup:

Wow thank you so much

to find the triangle size to put any square on point- divide the size of the block by 1.414 add seam allowance- round up to nearest whole inch (or half if you want) cut in half you have 2 of your setting triangles- to know how big your square will be when placed on point multiply the size of the block by 1.414- that gives you the size of the on point block- it also gives you the dimension of the diagonal of your original block....1.414 os a number that comes in handy ALOT! you will either multiply or divide with it lots.