439. Calculating the Size of a Sefer Torah - part 1
Tefillin, Mezuzah v’Sefer Torah 9:4
(Continuing from 9:3) Next, one makes a stick measuring 40 or 50 thumb-widths in length. Each thumb-width on the stick should be divided into halves, thirds and quarters, so that exact measurements will be possible, down to a quarter thumb-width. Each sheet of parchment is measured with this stick to determine its length. In this way, one can calculate the length of the entire roll.
Tefillin, Mezuzah v’Sefer Torah 9:5
One then takes two or three other sheets of parchment in order to compare the size of his writing. He writes a sample column of text. The height of the column will necessarily be 17 thumb-widths because three thumb-widths are left blank for a margin above the column and four thumb-widths are left blank for a margin below. The width of the column will vary based on the size of one’s handwriting. Similarly, the number of lines in a column of text will vary depending on one’s handwriting. The width of a line is left between lines.