The mini granny squares only take about 60” for each one. And you will need lots of squares. You can make them all at once, or over a period of time. They look pretty stored in mason jars.

This is easily adjusted for different sizes. The only really difficult part is figuring out how many mini granny squares you are going to need.

My baby blanket is 17 squares across and 19 squares high, which comes out to approximately 27” x 36”. And it used 323 squares.