If they are HSTs, google "magic 8 triangle method" for a helpful tutorial that shows how to make 8 HSTs at once.
So-called "pro" tip (ha!): using the formula will give you *exactly* the size you want, which is great unless you need to square a wonky, misbehaving hst. I learned to make them a tad bit larger by either sewing a scant 1/4" seam, or starting with a larger square and then trimming my HSTs down to size.