2g to 3g
This depends on which machine, 16T occupies about 2.5g, 16x about 2g, 17 and 16 are a system, then it is the same about 2.5g, and 18 upgraded to flyme9, to the official website to check the basic system will be about 300mb more each time, so 18 takes up about 3g memory
You can also view it yourself, go into the Settings, find about the phone, find the system version and click 7, the phone will open the developer mode, and then return to find the auxiliary function, find the developer mode, after entering to find the running services, you can view the occupation of the mobile phone system, I hope to help you