The confusion between “who’s” and “whose” is pretty much the same as with “it’s” and “its.” One is the contraction of “who is” or “who has” – the other is used to show ownership. Compared to one of our previous articles about “who vs. whom,” this topic here is much easier to understand. 

Who’s

“Who’s” is the short version for “who is” or “who has.” Luckily, this is the only meaning for “who’s.” If you’re unsure which one you ought to use, try replacing it with either “who is” or “who has.” If the sentence still makes sense and retains its meaning, stay with “who’s,” otherwise choose “whose.”

“Who’s staying at Beth’s house?”
(“Who is staying at Beth’s house?”)

“Who’s left the dirty plates on the kitchen counter?”
(“Who has left the dirty plates on the kitchen counter?”)

“I’m having dinner with an old friend, who’s staying in the city for the weekend.”
(“I’m having dinner with an old friend, who is staying in the city over the weekend.”)

“Who’s he talking to on the phone?”
(“Who is he talking to on the phone?”)

“She’s visiting her aunt who’s a big mansion in San Diego.”
(“She’s visiting her aunt who has a big mansion in San Diego.”)

Whose

“Whose” is a possessive adjective that describes the ownership of something (“belonging to whom”). You can also use it to express the association to a specific group or a received action. “Whose” usually stands before a noun. 

“Whose dog is barking outside?”
(The neighbor’s dog is probably barking outside.)

“Whose car blocked the crossroad ahead?”
(The older man’s car blocked it.)

“I met Charles yesterday whose wife sadly passed away last year.”
(Charles’ wife sadly passed away last year.)

“Whose keys are these on the counter?”
(They are my husband’s keys.)

“I met my mum’s best friend whose daughter went to Yale.”
(My mum’s best friend’s daughter went to Yale.)