As of March 2014, it costs $6.97 to mail a letter from the United States to England via the U.S. Postal Service's First Class Mail. The envelope cannot be any more than 15 inches long, 12 inches high and 0.75 inch thick, and the value of the contents cannot be any more than $400.
It costs $1.15 to mail a postcard from the United States to England. The postcard must not exceed 6 inches in length and 4.25 inches in height.
It costs $65.95 to mail a letter to England via the USPS Global Express Guaranteed service, which takes one to three days to arrive. A letter that fits into a flat rate envelope for USPS Priority Mail Express International costs $24.75 to mail to England, where it is likely to arrive in six to 10 days.