I'm asking because I'm a novice and probably will come up against this but couldn't you just do another round of single or even double crochet around the edges to make them closer to the same size?
Maria's right. Of course the yarns in my stash weren't all the same either. I used 2 strands of yarn when it was too thin to get a similar square out of it. That way, the squares were more or less the same. I had some squares that were a bit bigger than the others, but I did not put these together in the blanket and looking at it now I wouldn't know which were the bigger ones.
I can really recommend a project like this for depleting a stash! Good luck