One stamp is required to mail a letter of standard size from California to Arizona or to any other point inside the United States via the United States Postal Service. Non-standard letter sizes or those weighing more than one ounce demand additional postage.
A First-Class stamp for a 1-ounce letter costs 48 cents in 2014. Large flat envelopes cost 98 cents to send. For an extra $3.30, the identical letters can be shipped as Certified Mail from California to Arizona or anywhere else in the United States.
It costs $5.05 to send a letter by Priority Mail, which includes free tracking. Priority Mail Express Overnight costs $13.09. These additional fees may necessitate additional stamps or other printed labels indicating the fees.