How small and how big can a Torah scroll be?

The physical size of a Torah scroll can, in theory, vary greatly. The writing must be large enough to be readable by the naked eye, but a Torah could be written in very tiny letters on very thin parchment, which would make its total length very small. At the other end of the scale, a Torah could be written in very large letters on very large sheets of parchment, which would make its total length very large. No upper or lower limits are specified on the size of a page (a column) in a Torah scroll or on the total length of the scroll. In Bava Basra 14a (Shulchan Aruch, Yoreh Deah 272) we find that (if possible) the circumference of a Torah scroll should be equal to its height; but no upper or lower limits are given on the circumference or height themselves.