add_image_size – Can i Set 100% ?

Hey wordpress crew,

I am trying to add 100% to my featured images and cant work it out

here is what ive tryed

add_image_size( ‘feat-thumb-100’, 100%, 100% , true ); | Nope ??

and

add_image_size( ‘feat-thumb-100’, 100 . “%”, 100 . “%” , true ); | Nope

and finaly

add_image_size( ‘feat-thumb-000’, 100 . ‘%’, 100 . ‘%’ , true ); | Nope

Thanks for any help in Advance,

Best,

Connpr