If your quilt is 61"x72" it will depend on what you are using for backing.
Backing fabric that is 108" wide you will need 2 1/4 yds
2yds =72" with 1/4 yd more left over to attach to quilting frame.
Since the width has so much left over you will have enough if you want to use as binding.
If you are using regular 44" wide fabric you will have to piece it and it will take 4 1/3 yds. I think you could get by with 4 1/4 but I like to be sure I have enough. I hope this helps you and that it makes since. I like to have more fabric and do less piecing.