There is no quick formula to provide a reasonable estimate. Your post is lacking relevant details, such as how many pages are there, how many browsers and mobile devices the client expects to be supported, are there any forms, is there a database in the solution, and so on... You said "Complex" but did not describe what it means.
Just to test the design and layout, for example, can be as quick as 15 minutes per page, or as much as 1 hour per page, not to count functional test cases, or possibly more.
Additionally, if you are trying to automate, why are you automating, and what do you want to automate?