From the United States, it costs $1.15 to send a standard-sized letter that weighs 1 ounce or less to Germany. Postage costs more for heavier letters and letters sent in envelopes that aren’t the standard size.
The price changes a little for each additional ounce or fraction of an ounce. For example, the first extra ounce costs 98 cents, so a letter up to 2 ounces costs $2.13 to mail. The price goes up by 99 cents for each extra ounce.
The post office adds a nonmachinable surcharge of 21 cents to international letters with certain features, like an aspect ratio of less than 1.3 or more than 2.5, too much rigidity, or a delivery address that is parallel to the letter’s shorter dimension. USPS.com has information about how much it costs to send mail.