My living room measures 13 ft by 13 ft how do I get the correct measurements from that for the square footage to get the to order the right size rug I need carpet

Carpet only comes 12 feet wide by any length. So you would have to by 12 by 14 and cut one foot off the 14 side and carpet tape it to opposite side if you're not really good at home improvements then you need someone that is

My suggestion is to vist Lowe's and speak with of the professional staff. But the answer to your question is 13 times 13 equal 169 Sq feet

Or you can get 13 linear feet of carpeting that is at least 13 ft wide

13×13=169sq ft.