Yes it does. It is .20 cents more for a square envelope. You can look it up on usps.com. Right now it's .65 cents to mail a square envelope.
The cost of your mail is all about the weight of the package. the more that it weighs, the more it costs. The shape of the envelope is not going to change the price at all
"No, the cost of mailing a letter doesn't depend on the shape of the envelope but how much weight is actually inside the envelope. It's based on the weight."
In March 2018, the cost to mail a square envelope through the United States Postal Service (USPS) was based on its weight and dimensions. A square envelope that met the criteria for First-Class Mail would typically require additional postage due to its non-machinable nature. As of that time, the starting rate for a First-Class Forever stamp was $0.50, but non-machinable square envelopes generally required additional postage, often totaling around $0.71 or more, depending on weight.
$0.95 if it's a regular envelope; $1.50 if it bends easily and in a larger envelope; $2.12 if it's rigid or more than 1/4 in. thick and in a larger envelope.
The current postage cost for a USPS First Class Mail Letter (1 oz. ) is $0.49. Unless, the letter's weight is more than 1 oz. it is not more than that.
The cost to mail a padded 9x12 envelope varies based on the weight and the mailing service you choose. For domestic shipping within the United States, using First-Class Mail, it typically ranges from around $4 to $8. If you opt for Priority Mail, the cost can increase to approximately $8 to $12 or more, depending on the weight and service level. Always check the current USPS rates or any courier service for the most accurate pricing.
The cost would depend on the weight of the parcel. Big envelopes cost more than small envelopes of equal weight. You probably should go to your post office to mail this.
As long as the envelope doesn't weigh too much (If you're just mailing paper, then it probably doesn't) then no it doesn't cost more.
The postage rate to mail a 6x8 envelope in the United States as of 2014 is $0.44 if it is within the regulated weight. Additional costs may occur if it weighs more.
Yes, it is the same for the same weight. Both are considered 'oversized' mail or 'flats' and cost more than a normal business envelope. the current rate would be 88 cents for the first ounce and 17 cents for each additional ounce.
Letters sent by the royal mail with the Airmail service ( not you will need a special air mail envelope, these should be available from your local post office) will cost 56p to send to a destination outside of Europe. If the letter is heavier than 10g it may cost slightly more.
1 to 2 weeks or more