A legal-size envelope is an envelope that generally measures 9.5 by 15 inches. Legal-size envelopes are designed to store, mail or transport legal documents that measure 8.5 by 14 inches.
Paperboard, manila and other paper legal envelopes are used to mail documents through mail services such as USPS. Unlike standard envelopes, legal envelopes are large enough to accommodate many pages of a document. Legal-size envelopes are also suitable for mailing pictures and other documents that are ruined when folded. Some legal-size envelopes are constructed of thin plastic and are designed for storage and organization of legal documents for work and home purposes.