I use 3 1/2" and 4 1/2" (finished) blocks for a baby quilt. I also found a pattern here:
http://modernhandcraft.com/2014/01/i...rial-giveaway/ I ended up cutting the squares down to a 4 1/2" size. As the blocks were just too big for a baby quilt. But, they finish at 6" squares and should be a nice size for a young adult. (Also, you can just leave out the heart rows and make them all zig zags if you prefer.