Nakow, bandwidth is highly subjective. If strictly browsing lang (text and pictures), 5 mbps is ok.
But who actually does "browsing-only" activities when every few seconds, you end up watching a YouTube video or some sort of video streaming embedded in social media?
It also depends on what kind and how many devices you own. PS4? They're known to download game updates on their own and that will eat up your bandwidth quickly to the point of it being unusable to other users. You have a Steam account? A bandwidth hog as well.
How about movie streaming.... 5 mbps could probably support 1 HD stream.
Bottom line, bandwidth is all about user experience.... the higher, the better. You can still do a lot of things with 5 mbps, but be prepared to have poor user experience depending on your household's internet consumption.
Anyway, try using this simple bandwidth calculator. It's not by any means accurate but it will at least tell you what your average internet bandwidth should be.
Bandwidth Calculator: How Much Internet Speed Do I Need?