Based on 2015 rates, the cost of mailing a letter from the United States to Spain ranges from $1.15 (1 ounce) to $4.11 (3.5 ounces) per ounce. Large envelopes, which contain rigid or non-rectangular objects, range in price from $2.29 (1 ounce) to $35.08 (one pound) (64 ounces).
The United States Postal Service price list can be found at USPS.com. Spain is in price group 5 according to international pricing lists, which divide countries into groups. In addition, the online USPS international mail manual includes country-specific limits and regulations for Spain. For instance, corporate paperwork do not require a customs form, whereas samples of merchandise and promotional materials do.
