Square Envelope Postage
Square wedding invitation postage always includes the $0.49 nonmachinable surcharge, as does any other square letter. A 1 oz square invitation costs $1.31 instead of $0.82; at 2 oz it is $1.60.
Your answer
Nonmachinable letter
+$0.49 surchargeLetter postage plus the nonmachinable surcharge, because it has to be sorted by hand.
- Postage per piece
- $1.31
- 150 invitations
- $196.50
Stamps for each one
1 × Three-Ounce
That pays $0.09 more than needed. For exact postage, ask the post office counter to make up $1.31.
Why
- Square envelopes fail the aspect ratio rule: length divided by height must be between 1.3 and 2.5, and a square is 1. USPS rule
Save money: Switch to an A7.5 rectangle (5.5 x 7.5 in) and save $73.50 on 150 pieces, as long as the weight stays the same.
Rates last verified on
150 invitations: $196.50 in postage ($1.31 each, nonmachinable letter)
The aspect ratio rule
USPS measures a letter's length along the address and its height across it, then divides length by height. The result must be between 1.3 and 2.5. Sorting machines rely on that shape to stand a letter up the right way and find the address.
A square has a ratio of exactly 1. It can land on any of its four edges and the machine cannot tell which is the bottom. So squares are sorted by hand, and the surcharge covers the handling. DMM 101.1.2 lists this first among the nonmachinable features.
It is about shape, not size
A near-square fails too. A 5 x 6 in envelope has a ratio of 1.2 and pays the surcharge just like a true square. To pass, the long side must be at least 1.3 times the short side.
Square postage by size
Square envelopes fall into three groups:
Is the square worth it?
On 150 invitations the surcharge is $73.50. Next to the cost of the invitations themselves that is often a small line, and plenty of couples pay it gladly for the look.
If you would rather not, keep the square card and change the envelope. A rectangle tall enough for the card mails at the normal price, and once you are paying for a square anyway, a wax seal or ribbon costs nothing more.
Compare the options
| Option | Mail class | Each | For 100 |
|---|---|---|---|
| 5 x 5 square | Nonmachinable letter | $1.31 | $131.00 |
| 5.5 x 5.5 square | Nonmachinable letter | $1.31 | $131.00 |
| A7.5 rectangle (fits a 5.25 in square card) | Standard letter | $0.82 | $82.00 |
| 6 x 6 square | Nonmachinable letter | $1.31 | $131.00 |
| 6.5 x 6.5 square | Large envelope (flat) | $1.69 | $169.00 |
Questions and answers
Why do square envelopes cost more to mail?
Their length divided by height is 1, below the 1.3 minimum sorting machines need, so they are sorted by hand and pay a $0.49 surcharge.
How much postage for a square wedding invitation?
$1.31 at 1 oz, $1.60 at 2 oz and $1.89 at 3 oz for squares from 5 in to 6 1/8 in.
How many stamps does a square envelope need?
Enough to cover $1.31 at 1 oz. Two Forever stamps do it with a small overpayment.
Is there a square envelope that avoids extra postage?
No. Any square letter is nonmachinable. Only a rectangle with a long side at least 1.3 times its short side avoids it.
Does the surcharge apply to large square envelopes?
No. A square over 6 1/8 in is a large envelope, priced from $1.69, and the surcharge applies only to letters.