This measuring tape has the zero mark in the center of the tape, so you can start from the center mark on your canvas leader, and measure out to the ends. 

Developed with the frame quilter in mind. Double sided Measuring Tape and Centering Tape. Easily measure and center fabric Measuring Tape: 0"-120" (inches and metric) Centering Tape: 60"-0"-60".

From the middle, it extends 60 inches each direction. 

It is very convenient.