I am travelling on jetstar on 17th May 2018, need to know the baggage Allowed on Jetstar Airline
That depends what fare you have booked
20kg is fairly common.
No single item of baggage can weigh more than 32kg ( this is REALLY HEAVY)
See also size limits on bags.
Jetstar are pedantic about size and weight limits.
Carry on is 7 kg and free of charge. Any checked in luggage has to be paid for and you can purchase from 15 to 40 kg.
You can access then internet to ask on TripAdvisor, but not Jetstar's official website?
Be careful as some third parties in order to give you a "cheap" fare only quote the Lite price which includes only hand luggage. When you book you have the option of selecting how much luggage you want to pay for and this can be increased before checkin. However if you want to pay for luggage once you get to the airport then the amount has become a lot more.
Your booking confirmation will show how much luggage you have paid for.