Grid paper This is paper printed with a grid, a pattern of horizontal and vertical lines spaced at regular intervals. The resultant squares can be assigned numeric values, such as one foot each. Grid paper is usually printed with four or eight squares per inch in faint blue lines. These squares are ¼” or 1/8” in size, meaning that 4 boxes or 8 boxes equals one inch. It facilitates the drawing of straight, to-scale lines.
This photo shows the relationship of 1/8″ grid paper to the 1″=1′-0″ scale. Every two squares represents 3″. A large square (boundaried by the dark blue lines) represents 12″.
Read more about grid paper and sketching in my book, Drafting and Visual Presentation for Interior Designers.