Figure out the length of a roll of paper by knowing the diameter of the paper roll, the thickness of the paper and the dimension of the center hole. The stretch or softness of the paper does not factor in the equation. You can use this formula at home or in various industries to determine how much paper remains on a paper roll, how much carpet remains on a roll of carpet, how much fabric is left on a bolt or how much yarn or thread is on a skein.
Measure the diameter of the paper roll and the center hole using a tape measure. Write down the measurements.
Use the caliper to measure and write down the thickness of the sheet of paper that is rolled.
Multiply the roll of the diameter by 3.14159. This is the roll circumference in lineal inches.
Multiply the core diameter by 3.14159. This is the core circumference in lineal inches.
Add the two answers together and divide by 2. This is the average lap length in lineal inches.
Subtract the core diameter from the roll diameter. This is the thickness of the roll of paper.
Divide the thickness of the paper by the caliper of the paper. This is the number of paper layers on the roll.
Multiply the amount of paper layers with the average lap. This is the amount of paper on the roll in lineal inches.