Sub Floor Thickness for Tile

Hello Everyone,

thank you for reading/helping me out on this project. I am remodeling my bathroom. I ripped up the old floor tile and down to my sub-floor.

My sub floor is 5/8.
Floor Joists are 2x8 , 16 on center.

I plan on laying long tiles - 6" x 24"

I am trying to determine the thickness of plywood I should add to my existing sub floor, I plan on adding 1/4 backer board to the floor as well.

Any advise would be great, Thank you

Sub Floor Thickness for Tile