There is a relatively simple calculation you can use to determine how much is left on a roll of inkjet printable media, based on the diameter of the roll. Here’s how to determine the amount of material left on a roll, give or take an inch or two:
Roll length in feet = (0.06545/media thickness in inches) x (outer diameter squared – inner diameter squared)
All measurements are in inches, by the way.
For example, the outer diameter of the roll (core included) is 4 inches, the inner roll diameter is 3 inches, and the material thickness is .013 inches. There are 1,000 mils per inch, so the material in this example is 13 mils, or .013 inches thick. A 7-mil material would be .007 inches thick (7/1000):
(.06545/.013) x (42 – 32)
5.03 x (16-9)
5.03 x 7 = 35.24
Roll length remaining = 35.24 ft.