What is the size of a GUID?

For a table GUID uses for primary key and when we use it as a primary key so it creates a clustered index on that table. When we use GUID as clustered index then it decreases performance for inserting new data.

because there is 16 bytes binary data which is logically grouped by "-" sign.

for example

    12345678-1234-1234-1234-1234567890EF
    4bytes   2bytes 2bytes 2bytes 6bytes 

So its size 4+2+2+2+6 = 16bytes