Post Office Requirements

I've decided to add the US post office requirements for 1st class envelopes to my blog where I can find them!  (I just spent WAY too long searching the USPS site for this information.)  Since I make my own envelopes and card bases at times, I want to remember the ratio required to be classed as "rectangular".  And for pricing, I need to remember other things on this list.  SO, as of their web-site on 3/25/2017:

Standard Sized Envelopes

Envelopes must be rectangular to qualify for letter prices.  This means that the aspect ratio of the envelope (length divided by height) is at least 1.3 and not more than 2.5.

Size Requirements

	Minimum	Maximum
Height	3 1/2"	6 1/8"
Length	5"	11 1/2"
Thickness	0.007"	1/4"
Weight	None	N/A

Non-Standard Sized Mail - like square or vertical envelopes, lumpy or rigid envelopes, or mail with clasps, string, or buttons, cannot use their automated processing machines. Hand-cancelled mail is charged a non-machineable surcharge - equivalent to the price for mailing an extra ounce.

I've used these measurements to create a table for my own use.  

I make NO GUARANTEES that I did the math correctly, or that the numbers here represent current post office requirements.  I'm simply posting it here for your use, but strongly encourage you to double-check my math (rounded to 1/8" increments) and the current post office regulations for yourself!

 

NOTE that standard envelopes MUST be no more than 1/4" thick - between 1/4" and 3/4" must go as a "large envelope".  I recommend making yourself a template that has a 1/4" slot and a 3/4" slot to test your envelopes!!! 

Also note that if it weighs exactly one ounce on your scales, you better add postage for an extra ounce!  The post office will charge your recipient much more than that if they deem it overweight!

 

You may also be interested in this *.pdf of additional mailing hints that I came across - put together by TheMadStamper.  The postage rates are out of date, but much of the other information is still useful.  Here's a link to her blog post with a couple of useful videos about mailing our hand made cards.

Rectangle Requirements for U.S. Post Office

Envelope size (approximate card size)

HEIGHT	APROX. MIN. LENGTH	APPROX. MAX. LENGTH
3 ½”  (3 ¼”)	5” (4 ¾”)	8 ¾” (8 ½”)
3 ¾”  (3 ½”)	5” (4 ¾”)	9 3/8” (9 1/8”)
4” (3 ¾”)	5 ¼” (5”)	10” (9 ¾”)
4 ¼” (4”)	5 3/4” (5 ½”)	10 ½” (10 ¼”)
4 ½” (4 ¼”)	5 7/8”  (5 5/8”)	11 ¼” (11”)
4 ¾” (4 ½”)	6 1/4” (6”)	11 ½” (11 ¼”)
5” (4 ¾”)	6 ½” (6 ¼”)	11 ½” (11 ¼”)
5 ¼” (5”)	6 7/8” (6 5/8”)	11 ½” (11 ¼”)
5 ½” (5 ¼”)	7 ¼” (7”)	11 ½” (11 ¼”)
5 ¾” (5 ½”)	7 3/8” (7 1/8”)	11 ½” (11 ¼”)
6” (5 ¾”)	7 ¾” (7 ½”)	11 ½” (11 ¼”)
6 1/8” (5 7/8”)	7 7/8” (7 5/8”)	11 ½” (11 ¼”)