B4

The B4 envelope has dimensions of 353mm x 250mm, giving it a surface area of approximately 88,250 mm2. The maximum enclosure size is slightly less, around 244mm x 345mm. The B4 gets its designation from being part of the ISO 269 "B" series of paper sizes. It is between the B5 and B3 in size. The closest "A" size is the A3 sheet which the B4 envelope can accommodate when folded in half. While not as common as C4 or C5 envelopes, the B4 offers significantly more area and is useful for mailing catalogs, magazines, poster prints and other oversized documents. Compared to C4, the B4 is wider but shorter, providing a more squarish shape. The B4 is primarily used in Europe and Asia as it originated from the German DIN 476 standard.