That is a loaded questions! Depends upon tooo many things. Of course the pattern is number one, then the size and the number of pieces that have to be cut. Then each sew-er sews differently ~ some are speed demons and others are creepy crawlers. Then of course one should factor in un-sewing. ;(
A friend says that Eleanor Burns lied about 'a quilt in a day', because it took her a whole lot longer.