Frequently it is desirable first to determine the sizes of the margins. These depend on various considerations of the position and office of the MS., but more particularly on the size of the sheet and the character of its future environment[14] (see p. [351]).
The top and side margins may be of equal width—or the top may be a little less (see a, fig. [70]). Ample space should be allowed for the foot margin, which is generally about twice the width of the top, but may vary in different cases, according as the text falls short of or encroaches upon it (see pp. [352], [342]). For a plain foolscap sheet: sides (each) 212 inches, top (approx.) 2 inches, and foot (approx.) 4 inches, may be taken as suitable margins (fig. [65]).
The width of the sheet (1312 inches) less the two side margins (212 inches each) gives the length of the writing lines (1312 – 5 = 812 inches). One or two such lines are written experimentally in a suitable script (say, 516 inch), and the average number of words per line (four) is found.