Mailing Envelopes

How to choose mailing envelopes

Size

Sizes are short side by long side, in inches. A letter sheet folded in half measures 5.5 x 8.5 in and fits a 6 x 9. A flat 8.5 x 11 sheet fits a 9 x 12, and a 10 x 13 adds an inch each way for thicker stacks. Legal 8.5 x 14 sheets fit a 9.25 x 14.5 or a 10 x 15. For binders and kits, use an expandable envelope with a 1.5 to 4 in gusset.

Postage depends on size

USPS sorts mail by shape. An envelope up to 6-1/8 in high, 11-1/2 in long and 1/4 in thick mails as a letter. A larger one up to 12 x 15 in and 3/4 in thick mails as a large envelope, which USPS also calls a flat.

The 12 x 15.5 in size is half an inch longer than the large envelope maximum. Expandable envelopes packed thicker than 3/4 in also go over it. USPS sets a 3.5 x 5 in minimum for mail, so the 2.25 x 3.5 to 3.375 x 6 kraft sizes are coin and parts envelopes.

Paper, Tyvek or expandable

The flat kraft and white envelopes, the clasp envelopes and the jumbo envelopes are 28 lb paper. The Tyvek flats are 14 lb DuPont Tyvek. Colored Tyvek comes in black, green, red, silver and yellow in 9 x 12, 10 x 13 and 12 x 15.5 in. The First Class versions carry a printed First Class border. Kraft expandable envelopes are 40 lb paper and the Tyvek expandables are 18 lb.

Closure

• Gummed flap: moisten the gum and press it shut for a permanent seal.
• Self-seal strip: peel the release strip and press. No water or tape.
• Redi-Seal: press the flap down to seal. No moisture needed.
• Metal clasp with gummed flap: close it with the clasp to open and reuse it, or moisten the gum to seal it for good.
• String and button: the inter-department envelopes wind shut and open again.
• Ungummed flap: the jumbo envelopes have no adhesive. Close them with tape.
• Tamper evident: the 9 x 12 and 10 x 13 tamper evident Tyvek envelopes show OPENED in red once the seal is broken.

Buying by the case

Every price on this page is for one full case. Small kraft envelopes come 5,000 to a case, #10 business envelopes 2,500, flat paper envelopes 250 to 2,500, clasp envelopes 500 or 1,000, Tyvek flats 100, and jumbo envelopes 100 or 250.

Volume pricing comes off at checkout: 3% at 3 or more items in the cart and 5% at 6 or more. Orders of one or two items get free ground shipping in the US at $99 or more when the checkout shipping charge is $29.95 or less. Orders of one or two items with a product subtotal of $500 or more ship free when the checkout freight rate is $120 or less. Orders of three or more items get the volume discount instead of free shipping.

For pallet quantities, a standing order or a mix of sizes, send the SKUs, case counts and delivery ZIP on a bulk quote. The quote includes freight to your ZIP, and you can pay by card or ACH.

Request a bulk quote

Common questions

Related

• Packing list envelopes
• Bubble mailers
• Padded mailers
• Poly mailers
• Corrugated literature mailers
• Rigid mailers
• Mailer size chart

Letter and large envelope limits come from USPS Business Mail 101, Sizes for Large Envelopes and Flats and the USPS Quick Service Guide 201. Sizes, case counts, paper and Tyvek weights, closures, reuse and resistance notes come from the product listings.