Question

When to use whose vs who's?

Answer 1

Who's is a contraction of who is or, less commonly, who has.
Who's watching TV?
Do you know who's going to speak?
Who's ready to go?
Who's in the kitchen?
Who's this?
Who's already eaten?

Whose is the possessive of who or, somewhat controversially, which.
Whose book is this?
Do you know whose car this is?
I know a woman whose kids study there.
Whose side are you on?
An idea whose time has come.

Answer 2

does this help?

Answer 3

Who's is when you're asking: Who is?
And Whose is when you're asking if something belongs to someone^what she said :P

Answer 4

thx for summing it up.. xD