Types of Envelopes: 12 Kinds and What Each Is For
Envelopes differ by what they carry and how they close. Paper styles such as window, catalog and clasp handle letters and documents. Tyvek, expandable and tamper evident styles add strength or security. Bubble, poly and rigid mailers protect products and prints in the mail. Choose by what goes inside, then by size.
Types of envelopes at a glance
| Envelope | Best for |
|---|---|
| Window envelopes | Invoices, Statements, Bulk mail |
| Catalog envelopes | Flat documents, Catalogs, Reports |
| Clasp envelopes | Office files, Reusable storage, Internal documents |
| Inter-department envelopes | Internal mail, Routing documents, Repeat use |
| Tyvek envelopes | Light shipping, Water resistance, Important papers |
| Expandable envelopes | Thick files, Binders, Small items |
| Tamper evident envelopes | Legal documents, Sensitive papers, Chain of custody |
| Jumbo envelopes | Posters, Blueprints, Oversize documents |
| Bubble mailers | Small products, Fragile items, Jewelry and electronics |
| Poly mailers | Clothing, Soft goods, Lightweight orders |
| Rigid mailers | Photos and prints, Certificates, Do not bend items |
| Packing list envelopes | Invoices on cartons, Shipping documents, Warehouses |
Quick picks: what are you sending?
The 12 types of envelopes
Window envelopes
A window envelope shows the address printed on the letter inside, so nothing needs to be printed twice. The #10 size, 4 1/8 by 9 1/2 inches, is the US business standard and holds a letter folded in thirds.
Catalog envelopes
Catalog envelopes open on the short end and keep paperwork flat. Sizes such as 9 by 12 and 10 by 13 inches hold letter-size pages with no folding.
Clasp envelopes
A clasp envelope closes with metal prongs through a reinforced hole, so it can open and close many times. Many also have a gummed flap for mailing. USPS can add a nonmachinable surcharge to letters with clasps, so check the postage before mailing.
Inter-department envelopes
These reusable envelopes have a printed grid for routing names and a string and button closure. They move paperwork around a building without being sealed.
Tyvek envelopes
Tyvek is a spun polyethylene material that is light and very hard to tear, and it shrugs off water. It is a strong upgrade over paper when documents travel rough routes.
Expandable envelopes
Gussets along the sides let these envelopes open up to several inches deep. They carry thick files and bound documents that would split a flat envelope.
Tamper evident envelopes
The closure on a tamper evident envelope shows damage if someone opens it. Use them for sensitive documents where you need to see that the seal stayed intact.
Jumbo envelopes
Jumbo envelopes run up to sizes such as 22 by 27 inches. They carry large flat items without rolling them, and they cost more to mail because they fall outside letter and flat size limits.
Bubble mailers
A bubble mailer is an envelope lined with bubble cushioning. It protects small products with no box and adds little weight. See the bubble mailer size chart for numbered sizes.
Poly mailers
Poly mailers are light, water-resistant plastic envelopes with a self-seal strip. They suit products that cannot break, such as apparel. The poly mailer size chart lists common sizes.
Rigid mailers
Rigid mailers are made from stiff chipboard, so they keep photos, prints and certificates from bending. Many have a tear strip and a self-seal flap.
Packing list envelopes
These adhesive-backed plastic pouches stick to the outside of a carton and hold the packing slip or invoice. See the packing list envelope sizes.
Envelope sizes and postage
The envelope you choose can change the postage. USPS prices letters, large flats and parcels differently, so a thick or rigid envelope can cost more to mail than its weight suggests. The envelope size chart lists standard sizes in inches and millimeters with the USPS limits, and the how to address an envelope guide covers format and stamp placement.
Frequently asked questions
What are the main types of envelopes?
Common types include window, catalog, clasp, inter-department, Tyvek, expandable, tamper evident and jumbo envelopes, along with bubble, poly and rigid mailers and packing list envelopes.
What is the most common envelope size?
In the US, the #10 business envelope, 4 1/8 by 9 1/2 inches, is the standard for letters folded in thirds.
What is the difference between a catalog and a booklet envelope?
A catalog envelope opens on the short end. A booklet envelope opens on the long side, which makes it easier to stuff by machine.
Which envelope is best for shipping small items?
A bubble mailer suits small or fragile products, and a poly mailer suits soft goods that cannot break.