6.5 x 6.5 Square Envelope Postage
A 6 1/2 in square envelope is over the 6 1/8 in letter height limit, so it is a large envelope (a flat): $1.69 at 1 oz, $1.98 at 2 oz, $2.27 at 3 oz.
Your answer
Large envelope (flat)
Costs more than a letterPriced as a large envelope, which costs more than a letter.
- Postage per piece
- $1.98
- 100 invitations
- $198.00
Stamps for each one
1 × Three-Ounce + 2 × Additional Ounce
Why
- This is taller than 6.125 in, which is past the letter limit, so it is a large envelope (flat). USPS rule
Rates last verified on
100 invitations: $198.00 in postage ($1.98 each, large envelope (flat))
Not a letter, so no surcharge
This size surprises people in both directions. It does not pay the square-envelope surcharge, because that surcharge only applies to letters and this is not one. But the large envelope price starts higher than a letter with the surcharge would cost: $1.69 against $1.31 at 1 oz.
The aspect ratio rule does not apply to large envelopes at all. A square flat is as acceptable as a rectangular one.
Large envelopes have their own rules
A large envelope must be flexible and evenly thick. A rigid one, or one with a bump that changes its thickness by more than 1/4 in, is charged as a package, at package prices. A thick board backer or an acrylic invitation in a 6 1/2 in square envelope is exactly that case.
A wax seal or ribbon, on the other hand, adds nothing here as long as the envelope still bends and the bump stays under 1/4 in.
Stamps for a large envelope
There is no single large-envelope stamp at most counters. At 1 oz the $1.69 price equals the 3.5 oz letter price, so one Three-Ounce stamp plus one Additional Ounce stamp covers it exactly. Each further ounce is one more Additional Ounce stamp up to 8 oz.
If the stamp cluster spoils the look, a post office can print a single postage label for the exact amount.
No 3.5 oz cliff
One thing is simpler with a large envelope: weight steps run evenly all the way to 13 oz. There is no jump at 3.5 oz the way there is for letters, because you are already on the large envelope price list.
Compare the options
| Option | Mail class | Each | For 100 |
|---|---|---|---|
| 6.5 x 6.5 square, 1 oz | Large envelope (flat) | $1.69 | $169.00 |
| 6.5 x 6.5 square, 2 oz | Large envelope (flat) | $1.98 | $198.00 |
| 6 x 6 square, 2 oz | Nonmachinable letter | $1.60 | $160.00 |
| 6.5 x 6.5 square, rigid, 2 oz | Package | Package price | - |
Questions and answers
How much postage does a 6.5 x 6.5 envelope need?
$1.69 at 1 oz, $1.98 at 2 oz and $2.27 at 3 oz, at large envelope prices.
Does a 6.5 inch square envelope pay the nonmachinable surcharge?
No. The surcharge applies only to letters, and this size is a large envelope.
Is a 6 inch or 6.5 inch square cheaper to mail?
The 6 in square. At 1 oz it costs $1.31 with the surcharge, against $1.69 for the 6 1/2 in square.
Can a 6.5 inch square invitation be rigid?
Not at large envelope prices. A rigid large envelope is charged as a package.