How much usable fabric is in your 45" width. I don't know of many fabrics that are truly 45". Always get more. Even experienced quilters sometime miscut and you don't want to end up with not enough squares.
NEVER assume the 45" is correct. I have had fabric from same line and same company vary from 40" to 46" so you have to measure the width. Then there is the possibility of some shrinkage.