You may use the USPS rate calculator to calculate postage for domestic or international mail: http://postcalc.usps.gov
The Proper Way to Mount a Rural Mail Box
Mount your mailbox on the right side of the road in the direction the letter carrier travels on his or her route.
If you are mounting your mailbox on a rural road (figure 1), mount it so the bottom of the mailbox is between 42 and 48 inches from the surface of the road. (If the letter carrier has to drive off the road, mount it so the mailbox is between 42 and 48 inches above the ground where the tire rolls.) A height of 47 inches is actually the preferred height by local postal officials.
Mount the mailbox far enough off the side of the road where it won't get hit. Remember that school buses and trucks have mirrors that stick out on the right side that could hit your mailbox.
We recommend putting your street number on both sides of the mailbox to make it easy for the post office and emergency vehicles to find your home. Use at least 1" tall reflective numbers (2" or 3" tall numbers will be much more visible). Be sure the flag will not cover up any of your numbers.
You may also add your name to the mailbox if you like.
If your mailbox is on a street with a curb (figure 2), mount the mailbox so the bottom of the mailbox is 42 to 48" from the street. (47" is the preferred height).
Mount the front of the mailbox 6 to 9" from the curb.