(of paper) measuring approximately 8½ × 11 inches (22 × 28 cm).
(of office supplies and equipment) made for holding letter-size sheets of paper.

Compare legal-size.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for letter-size

Historical Examples of letter-size

  • The circulars are printed on half a sheet of letter-size typewriting paper, sold in several stationery store in large quantities.

    Mary Louise and the Liberty Girls

    Edith Van Dyne (AKA L. Frank Baum)