How many characters are there in a GUID?

From MSDN:

A GUID is a 128-bit value consisting of one group of 8 hexadecimal digits, followed by three groups of 4 hexadecimal digits each, followed by one group of 12 hexadecimal digits. The following example GUID shows the groupings of hexadecimal digits in a GUID: 6B29FC40-CA47-1067-B31D-00DD010662DA

From Wikipedia:

Often braces are added to enclose the above format, as such:

{3F2504E0-4F89-11D3-9A0C-0305E82C3301}

So a total of 38 characters in the typical hexadecimal encoding with curly braces.

-Adam

As Adam mentioned from the MSDN quote, UUIDs are 128-bit values. This means that they take 16 bytes of RAM to hold a value. A text representation will take 32 bytes (two bytes for each single byte), plus the 4 hyphens, plus the two brackets if you want to include those; this amounts to 38 bytes.

Just keep in mind that if you are exposing UUIDs to users of your software, they may provide the UUID with or without the brackets. If you're storing the value anywhere, it's best to store it as the 16-byte binary representation. If you are interoperating with other UUID implementations, you may want to use the basic text format for interoperability, since different implementations do different things to the order of bytes when storing a binary UUID value.