View this handy envelope guide to quickly find the type of envelope that is the right size and capacity for your mailing. For a complete guide to envelopes of all kinds and helpful postal regulation information, download the PDF file of the The Envelopery provided by Williamhouse.

For best results, envelopes should be at least 1/2" longer than the longest insert. Recommended clearance from top to bottom is no less than 1/4". However, when inserts are thick or bulky, extra allowances must be made. Minimum size envelope as specified by postal regulations is 31/2" x 5".
1. If address is to appear on the envelope, a regular, full-face envelope should be used.
2. For enclosure addressing, use a type of window envelope.
3. If insertion is to be done by machine, use an open side envelope.