If you think filling out an American 1040 income tax form is bad,
you should try addressing a letter in Germany?

Where to write the address on an envelope when using the German mails.
This diagram is a translation and summary of several diagrams and explanatory pages
on the Deutsche Post (German Post) site.
All measurements/distances are in millimeters.

For general information about formatting addresses when mailing to Germany, you should see the Germany section of the International Mailing Address Formats page.

Look up postal codes (German equivalent of what in the U.S. are "zip codes")

• in German (requires Javascript)
  
• for English speakers.

Some additional notes:

• Don't underline the postal code and town/city.
• If you type the address in fixed-width print, ideally you should use a type size with 10 or 12 characters (width) per inch.
• If you print the address in a proportional font, the characters should be separated horizontally by .3 to .5 millimeters.
• If you print an address in a proportional font, between postal code and town/city a separation of 3 to 5 millimeters is needed, as between street name and house number. The font size used should be between 10 point and 20 point, with characters between 2.5 and 4.7 millimeters high (x-height.)
• The left edges of each line of the address should be even. (Use even left margin.)
• You really should skip down a line, but not more than 10 millimeters (.39 inch), between the street address and the postal code + town/city.
• A list of approved colors for envelopes.
• More information on how to format an address.

I would tell you more of these guidelines instead of summarizing and skipping so much, but when I think about how much more there is to say on the subject I feel very tired.

Disobeying these rules is not likely to get your letter thrown out in the trash, but it may confuse the address-reading machines and cause your letter to travel slowly through requiring human processing. Perhaps your letter could even go to the wrong address (but probably not.)

Really we should be glad that Deutsche Post has told us in such great detail how to best please their machines. Probably every country's postal machines have as many fussy quirks and details that one should consider for best results. It is only unfortunate that to remember so many machine quirks and machine preferences, we probably need to be machines ourselves.

International Mailing Address Formats

The page you are now looking at is a little appendage to the International Mailing Address Formats page.

AskOxford: Writing Letters in German

Includes some general information on address formats, honorifics, and abbreviations.

The Post Office - The German Way

"Dealing with the typical large post office in Germany can be confusing..."

"The New English-German Dictionary"

German-English dictionary online, with option to download software to your PC. Pretty good.