I'm designing a database table and asking myself this question: How long should the firstname field be?
Does anyone have a list of reasonable lengths for the most common fields, such as first name, last name, and email address?
W3C's recommendation:
If designing a form or database that will accept names from people with a variety of backgrounds, you should ask yourself whether you really need to have separate fields for given name and family name.
… Bear in mind that names in some cultures can be quite a lot longer than your own. … Avoid limiting the field size for names in your database. In particular, do not assume that a four-character Japanese name in UTF-8 will fit in four bytes – you are likely to actually need 12.
https://www.w3.org/International/questions/qa-personal-names
For database fields, VARCHAR(255) is a safe default choice, unless you can actually come up with a good reason to use something else. For typical web applications, performance won't be a problem. Don't prematurely optimize.