Is Your DIY Envelope Mailable? Here are the USPS Guidelines for Handmade Envelopes

I’m fairly sure that I have made every mistake that it’s possible to make while trying to mail my handmade envelopes through the US postal system.

I’ve been upcharged for mailing a square envelope.

I’ve been upcharged for mailing an envelope with the address written in portrait rather than landscape format.

I’ve been upcharged for making my envelope out of super stiff upcycled cardboard.

I’ve been upcharged for putting handmade pinbacks or other fun treats in my envelopes so that they’re uneven.

You CAN mail handmade envelopes through the US postal system without paying extra, and you CAN even be a “little” creative with them! Here are the USPS’s current regulations for envelopes, and ways that you can work with them while still sending handmade.

Allowed Shapes and Sizes for Envelopes

As long as you play by the USPS’s rules for the size, shape, and weight of your letter, you can have a little bit of fun with your envelopes.

• Don’t make your envelope too heavy. The entire letter, contents and all, cannot weigh more than 1 ounce, says the post office. That is apparently the weight of four pieces of paper! I sometimes send a whopper of a letter to a friend, so I’m positive that I have violated this weight rule numerous times with no consequences. But better to be safe than pay extra postage, I suppose.
• Your letter must be at least .007″ thick. That’s the thickness of an index card, so it shouldn’t be hard to achieve.
• Your letter cannot be more than .25″ thick. That’s quite thick! But if you plan to include lots of filler inside your envelope, consider how the material you use for your envelope will also affect its thickness.
• Your envelope must be a rectangle with a landscape alignment. The post office charges extra for square envelopes, and for envelopes where the stamp and address make it clear that it’s to be held and read portrait-style, with an alignment that is taller than it is wide. I am still incandescent with frustrated rage when I think about that one time, 20+ years ago, when I obliviously took a whole stack of homemade wedding invitations, sealed in black envelopes aligned portrait-style, with the addresses written in silver, to the post office to mail.
• Your envelope can be a nonstandard size, but must fit within a specific range of dimensions and aspect ratios. An envelope can be 5″ to 11.5″ long and 3.5″ to 6 1/8″ tall, and must also have an aspect ratio of 1.3 to 2.5. That aspect ratio is tricky! It means that you can’t, as one example, have an envelope with the maximum length and the minimum height. Here’s an aspect ratio calculator to help you with the math.
• Envelopes must have 90-degree corners, but you may slightly round them.
• Your envelope cannot have any rigid, lumpy, or bumpy parts. There is some leeway for this rule, allowing you to mail items the approximate size and density, in particular, of credit cards and tokens without paying extra postage. Otherwise, you have to pay extra to mail letters that have clasps or other rigid items on or in them.

Allowed Colors and Embellishments for Envelopes

It’s SO tempting to craft a stand-out envelope in an unusual pattern or color. But the USPS is as picky about what your envelope looks like as it is about what size and shape it is.

• Your envelope must be paper or cardstock. You cannot make an envelope out of fabric, vinyl, wood veneer, leather, plastic wrappers, duct tape, or any of a million other creative and awesome materials.
• Do not use paper with a bold pattern for your envelope. You don’t want paper that calls more attention to it than your address does, lest the sorting machine be unable to actually find the address amongst all the noise.
• Don’t use an envelope with lots of texture, especially uneven textures like embedded glitter or flower petals, etc. This rules out all kinds of great ideas for handmade papers with inset embellishments, but it’s worth it for your envelope to have a smooth ride through the system.
• Don’t use shiny paper for your envelope. Again, it’s all about that machine that reads addresses. The USPS does not outlaw, however, clear mailing tape with a glossy exterior.. I actually do usually cover my etsy mailing labels with that tape and the post office police haven’t nabbed me yet!
• You can use colored paper for your envelopes, but the color should be subtle with a lot of contrast between the color and address.
• The envelope’s embellishments can’t be “lewd” or “filthy.” This feels more than a little loosey-goosey to me, but I guess the postal worker knows porny mail when they see it! Probably better to avoid stamping tiny penises all over your envelope…

Let’s talk addresses.  You can be a little fun and creative with how you address envelopes, as long as you keep the address legible and formatted in the standard way.

• Use at least 10-point font, whether you’re typing or handwriting your address. 10-point font is very small–smaller than the font of most novels!–so this one shouldn’t be hard to do.
• Left-justify the address. No centering or cute spacing allowed!
• Don’t write the address at a slant or on a curve. The USPS charges extra money for an envelope with a portrait rather than landscape format. Other than that, they don’t want you to mess with the address alignment AT ALL.
• The best ink choice is black, although the USPS does allow for most ink choices that contrast well with your (light) envelope color. The USPS specifically forbids white writing on a black envelope.
• Don’t write anything, whether it’s a cute message or a scrap of poetry, below the zip code.
• Addressing an envelope with a fictitious name or title is technically illegal. I don’t know why the post office would have a problem with me addressing a birthday card to my niece as “The Queen Wizard of Dinosaurs and Dump Trucks,” but it’s literally written into their mailing standards, sooo…

My personal rule of thumb these days is that the more I love my letter and want it to reach its destination, the more standard I make the envelope. If you’re just playing around with some fun, low-stakes pieces, feel free to experiment with your most creative choices. If you really want your piece to arrive safely and on time, however, make you DIY envelopes just a *little* bit creative.