It depends on the number of processes running in the background, opened by the user and always-on features. Please bear in mind that certain apps and processes are always running in the background including radio networks, social media and telephony, among others. Therefore, not all of the RAM is available to the user straight out of the box. Moreover, as user installs more and more apps while using the handset, as it is intended to, the RAM keeps getting filled. Therefore, do not be surprised when you see only 2GB or less RAM available when you have a 4GB handset.