How long can your name be on your family register?

When you become Japanese, you need an official "Japanese" name for you newly created 戸籍 {koseki} (family register). Contrary to popular belief on the internet, this does not necessarily mean you need to abandon your original name. It does, however, mean you need to transcribe your name into the scripts used by the language of the land, Japanese: all or a combination of ひらがな {hiragana} & カタカナ {katakana} (Japanese syllabet) and/or 漢字 {kanji} (Japanese-style sinograms). So even if you keep your original name, you will still need to adapt it to the script of the land. This is called "transcribing." Transcribing is usually more of an interpretation of either the original spelling or pronunciation, rather than an exact 1-to-1 mapping. This is because there is often more than one "correct" way to transcribe a name, and also due to compromises you need to make for sounds that exist in one language that don't exist in the other.

This is pretty standard around the world: if you officially register your name in countries that use Cyrillic for their official language, you will probably need to convert your English to a Cyrillic one, and some of the sounds will be lost. Likewise if you have to transcribe to Arabic or Hindi. When people with non-English names immigrate to America or the United Kingdom, they must transcribe their name to the English alphabet. Despite English's versatility, it can't perfectly represent the spelling and pronunciation of a lot of names out there. Even Europeans find they must abandon the acute accents and umlauts and other diacritics on their name which they would consider critical to their name when they adapt their alphabetic name to the simple 26 letters of English.

When foreign names are transcribed into 仮名 {kana} (Japanese syllabet), they often end up longer than the original foreign name, especially if the foreign name contains long clusters of consonants — something that isn't really possible to represent in Japanese. Additionally, a Japanese character is often the width of two "n"s in English, so each character is usually wider than the typically English alphabet character.

The problem with making a name too long is that most forms — both paper and computer — expect a "Japanese name" to be a typical length, even though there is technically no limit to the length of a name on a 戸籍 {koseki} (family register). So what is a typical length?

seven characters or more is labeled as "7"

The vast majority of names are four characters long (either syllabet or sinogram), followed by names that are five characters long.

Of those four character names:

• 35% are combinations of two character family names with two character given names
• 8% are one character family names with three character given names or vice versa

The next most common length is five character names. Of these five character names, the breakdown of family name length to given name length is as follows:

of the ~28.5% of names that are five characters total, this is the family/given length split

In other words, those who have a three character family name are most likely to have a two character given name, and the next most popular combination is a three character given name with a two character family name.

Less than 0.5% of the Japanese citizen population (presently in 2012, that's about 127 million people) has a name that is seven characters or longer. Of those, we can probably guess that the majority of these names are of foreign origin; as the previous data seems to indicate the "threshold" seems to be five characters: if you have a family name that is three characters long, you're unlikely to name your child with a name that has more than two characters.

However, there are cases of super long Japanese names that are legally registered. The longest known Japanese name to be registered with the 戸籍 {koseki} (family register) system is seventeen (17) characters: a two character family name and a fifteen (15) character given name:

野田 {NODA}　江川富士一二三四五左衛門助太郎 {Egawa fuji hifumishigo zaemon no suke tarō}

Looking at his given name, you can see that a lot of the components are often standalone men's names, and there is a numeric run ("12345") in the middle. I'm guessing that in day-to-day life he probably used the nickname "Tarō".

The longest name of somebody who is currently alive totals eleven (11) characters, with a two character family name:

藤本　太郎喜左衛門將時能

And there are currently two known (though there may be more) living examples of Japanese citizens with ten (10) character names — again, with two character family names:

• 燕東 海林太郎兵衛宗清
• 根本 寝坊之助食左衛門

All of these examples are common fodder for "believe it or not" trivia shows on Japanese television; after revealing their names, they usually run a special showing how difficult it is to use these full names in real life.

Most forms, both paper and digital in Japan assume that a name is a maximum of six — sometimes seven — characters in length. For paper forms, there will often be a box for each character of the name rather than a line, so you will run into problems if your name exceeds six or seven characters as there literally won't be enough boxes for all the characters in your name.

What name you choose for your Japanese name is your right and your choice. It's good to know, though, what the longest name is that you can choose before running into difficulties using it.

For the easiest time, pick a name under seven characters.