If you are a historical lover you need to have 2 days 1st day for mehrangarh and its market under the fort 2nd day for masuriya pahadi and umaid bhavan palace mainly these are the attractions at jodhpur
do try all the street foods of jodhpur thanks!
I think you'll be needing two days as there are many places to visit there. Mehrangarh fort itself takes 3- 4 hrs and other places like ghanta ghar, ranisar lake, umaid bhawan etc. takes time also so it will take 2 days to explore and discover the real beauty and culture of jodhpur. But if you're just have came for sight seeing than 1 day is enough for you to visit Jodhpur