Writing paper size is a term used to describe the standard sizes of paper used for writing and printing. The most common sizes are foolscap (8 letters), demy (4 letters), ROYAL (5 letters) and CAP (3 letters). Foolscap is the largest size, measuring 8.5 x 13.5 inches, while demy is slightly smaller at 8 x 13 inches. ROYAL is the next size down, measuring 7.5 x 11.5 inches, and CAP is the smallest size, measuring 7 x 10.5 inches.