Originally Posted by
MadQuilter
You may be able to "block" the block by using starch and a steam iron. I have pressed some blocks into submission and pinned them to the correct size on the ironing board. Not sure what the fudge factor is though. Sometimes the only option is a do-over. Like the other comment said: Wait until all of your blocks are finished. By then you will have gotten more experience too and it may be clearer why the block is off.
A Youtube tutorial says the fudge factor is 1/8". I've just finished 20 blocks for a red and white sampler quilt and when measuring and squaring up, I realized I had some problems, too. Two had points with not enough seam allowance so I replaced a square on one and completely remade the other. When I discovered most of my blocks were 12 1/4, I trimmed the others down to get in that ball park. I'd never thought or heard of adding a tiny amount but it's something I'll keep in mind.