As per to my experience 7 to 8 days.
1 Jaipur 2:- Bhangarh
3 and 4:- Udaipur and chittorgarh
5:- Ajmer sharif and pushkar
6 :- Jodhpur
7:- Sand dunes at jaisalmer 8 :- Bikaner
2 days for jaislmer
2 days for jodhpur
3 days for jaipur 2 days for bikaner
2-3 days for udaipur some day for ranthmbhor and ajmer I think 10 to 15 days are sufficient for rajasthan.
If you want to cover the culture and explore some more than the rest of us do , I would suggest a 15 day trip.
Else, if you want to just touch the surface you can do it in 10 days.
Major places would be :
Jaipur
Udaipur
Jodhpur
Jaisalmer
Bikaner
Ideally, 10-15 days can prove to be enough for a decent trip to Rajasthan. Major places like Jaipur, Jaisalmer, Udaipur, Jodhpur, Pushkar, Mount Abu, Bikaner can be covered during the trip. https://www.tripoto.com/rajasthan/tour-packages