Overhead changing varchar(2000) to text

Hi!

I do have several tables that uses varchar(2000) as store for remarks.
Lately, one customer need to store more than 2000 characteres, and I'm
considering changing from varchar(2000) to text.

What is the overhead?

Is there any place where I can learn about storage impacto for each data
type?

Thanks,

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Atenciosamente,

Edson Carlos Ericksson Richter