The best way to determine the length of scale that you required is to measure it.
Just follow the procedure to measure the "TRAVEL LENGTH" of the scale that you need.
(The physical length is 142mm(5.6inch) longer than the travel length of the scale, e.g. travel length is 820mm (32.28inch), physical length is 962mm (37.87inch).)
(We always mention the travel length for DRO as it is a more important piece of information than the physical length.)
1) Move your X axis to one extreme end and make a marking.
2) Move to the other extreme end and make another marking.
3) Measure the distance between the 2 marking, this is the TRAVEL LENGTH.
4) Select the correct travel length from our available list of travel length.
(E.g. you measure 780mm (30.7inch) travel length, the nearest is 750mm(29.5inch) or 820mm (32.28inch), we will choose 820mm(32.28inch), so that it will cover the entire travel distance).
5) Do the same for the other axis/axes.