When I first started quilting, a fabric shop gave me a little plastic measurement card for backings. It reads as follows:
Twin lining 5 1/4 Yds. 2 1/2" binding 3/4 Yd
63 X 87
Double 5 1/4 Yds 2 1/2" binding 3/4 Yd
78 X 87
Queen 7 1/2 Yds 2 1/2" binding 7/8 Yd
84 X 92
King 8 yards 2 1/2" binding 1 Yd
100 X 92
Your Rail Fence is beautiful---Love the colors!