In cases where documents are kept loose or stored in non-standard storage containers, it may be easier to calculate the amount of paper to be scanned based on a ruler measurement.
The average sheet of paper is 0.05 to 0.10 millimeters thick depending on the gauge, but a good rule of thumb is approx 175 sheets of paper per inch. That means for every foot of paper, you will have approx. 2,100 documents. If your documents are tightly packed, you could have up to 200 sheets per inch, or 2,400 documents per foot.