The U.S. Postal Service offers an online calculator that allows you to determine exactly how much postage a given envelope needs. The size, shape and destination of the letter help to determine the required postage.Continue Reading
Select a destination for your envelope using the U.S. Postal Service postal calculator. All domestic destinations are listed under "United States," and all other countries to which the U.S. Postal Service delivers mail are also listed.
Enter the ZIP codes of both the sender and the recipient.
Enter the date for intended mailing as well as the time of day the envelope is to be mailed.
Click on "Letter" or "Large Envelope," depending on the size of the envelope.
Enter the weight of the envelope in pounds and ounces.
Click on the shape of the envelope if mailing a small envelope. Choose any Priority Mail options desired. If Priority Mail is not required, click "Display all options" at the top of the Priority Mail page to see standard first-class mail costs.