It depends on what you do with your pc, how much you have open at once etc. It can be yes. Right now I'm running an i5 with 8gb of ram, I have 2 chrome windows open with 31 tabs between the 2 windows, notepad, calculator, realtemp, task manager and a chat messenger open. Nothing overly tasking, no big applications just a bunch of little stuff open. My ram usage is at 5.29gb out of 8gb. If I only had 4gb it would be using the swap file heavily on the hard drive causing slower overall performance (sluggishness).
Try opening task manager and look at your system performance to see how much ram you're using. If it's close to 3.5gb or more a lot of the time you could use more ram.