Not any measurement you're going to be happy cutting.
The Friendship Star block, which is the name of the block you described, is here.
http://www.quilterscache.com/F/FriendshipStarBlock.html
As you can see from the picture in the link, this block is based on a 3x3 grid, which does NOT divide evenly into 8".
If it were a 7.5" or 9" or 10.5" or 12" FINISHED block, it would have worked out perfectly.
How about a nice Sawtooth Star block - that's on a 4x4 grid, and would work wonderfully if you're trying to make an 8" FINISHED block.
It's a very easy block to make.
Here are cutting and sewing directions:
http://www.quilt-lovers-guide.com/sa...ilt-block.html