Motor count values to distance

I have a drive sending me a value of its encoder. This clocks uo from zero to 1024 and back for every rotation of the motor. What I want to do is use this value and convert it into a value for length using the multiple turns of the drive (encoder) but for the life of me I have no idea how to approach doing this. I have a Siemens S7 1500 PLC
Has anybody else done any thing similar?
Any help appreciated

Assuming you are getting the encoder position via fieldbus of some sort.
You need to be refreshing at least a couple of timer per rev at max speed to capture turns.

Record the position before moving
Use the direction and increment turns every time the value crosses 512
Position = rotations *1024 +current position - start position

What drive is it?