If the front of your quilt is mostly white, be very careful adding color to the back since it might show thru the batting. To make a 9" pinwheel, you will need to make four 4.5" finished HST. Need two sets of 5.5" squares. You get two HST per square and you need 4 HST to make a pinwheel so half of 9" is 4.5" Remember, these are finished sizes.