You can use any number of fabrics you choose in a 9-patch quilt. Every square can be different if that is what you want. The total amount of fabric will depend on several things - the size of each patch in the 9-patch, the finished size of the quilt that you want, and whether you want to put borders on your quilt. If you answer those questions, we can give you a rough idea of how much total yardage you will need.