The size of DL in envelopes is 8.8 inches, or 220 millimeters, by 4.4 inches, or 110 millimeters. According to Total Office Solutions, DL in envelopes stands for dimension lengthwise in German.
Total Office Solutions indicates that international envelope size is based on the envelope's ability to accommodate an A-size sheet whose basic measurement is 917 by 1297 millimeters. These envelope sizes are classified as C-Series and include C3, which holds an A3 sheet, C4 which holds an A4 sheet, C5 which holds an A5 sheet and C6 which holds an A6 sheet. However, the DL envelope is different in that it doesn't hold any unfolded A-size sheet.