Raid Question

[lwfitz]

Maybe I should know this already but....
I have a file server with eight 4tb drives in raid 5 giving me a total of 26tb (16tb used).
I'd love to expand this storage and move to larger drives and hopefully not start from scratch.
What I would like to know is, if I start swapping out drives with a couple 10tb drives will I get stuck only getting to use 4tb of each 10tb drive or will I gain
more of that drive space as I swap out more and more drives for 10tb drives. That feels like a really lobg run on sentence 

Does this make sense?