Question: how much does it cost to mail a first class letter to puerto rico?
Answer: Sending more than 3.5 ounces to Puerto Rico or sending large envelopes to Puerto Rico. Below are the rates for sending a large envelope ("flat") to Puerto Rico. The maximum weight for a standard letter is 3.5 ounces, so use a flat if you're sending more than 3.5 ounces. The base rate for Puerto Rico is $1.00.