Identifying the printer paper roll size is possible in three ways, which have been explained here:
1)  Measure the previous roll size with the help of a measuring scale to check the roll width and diameter, which will be easier for you to confirm the size of the new thermal paper roll
2)  Depending on the model of the thermal paper printer, you can easily do a Google search for the most compatible thermal paper roll and purchase it from Graphic Tickets & Systems.
3) Another way to make sure that you buy the correct thermal paper rolls is to measure the printer machine. Although the printer's width will be the same as the thermal paper rolls printer, the printer's groove will match the thermal paper roll core. By matching all these measurements, you can be sure that you are getting the correct thermal paper roll.