Ubuntu system font too small

After a reboot my Ubuntu system font has gone very small. This includes window headers, windows and terminal.

Any ideas what has caused this and how I can resolve it?

Solution 1:

To solve this problem, go to Applications->Settings->Appearance then goto DPI and uncheck or turn off "Custom DPI setting". Evidently, something causes that to activate during a [faulty] update.

Solution 2:

I had this exact same problem on my machine.

I went into Universal Access in system settings and switched "Large Text" on, then back off. After turning it off, the text went back to it's normal size and all was well.