The tools on the left and right are too small. How can I make them bigger?

Each tool is like 1mm in height and width. It's much smaller than my cursor even.

Edit -> Preferences -> User Interface : Symbol size

They will get bigger, but perhaps not big enough for your screen size, then. Inkscape 0.93 is supposed to solve the issue with hidpi screens.

It doesn't work. It's still too small. I don't even see a difference in it even though I made it larger.

I've got a 4K and 8K monitor. It looks horrible on them both.

I've got Inkscape 0.92.1 r15371 on my computer.

This is the newest one. I checked for updates again now and there isn't any new updates.

I know, Inkscape 0.93 is still in development. If the setting doesn't help, you may need to wait, or try out a development version, or use a smaller screen, or learn keyboard shortcuts.

See also:
http://www.inkscapeforum.com/viewtopic.php?f=29&t=23251
http://www.inkscapeforum.com/viewtopic.php?f=5&t=19210

Here someone claims they have a solution:
http://forum.inkscapecommunity.com/index.php?topic=479.0
(I can't comment on if it's working or not, it might well be dangerous. You are warned.)

Okay thank you!

I will wait for the next update then and try again.

The next update will be 0.92.2, which fixes some crashes on Windows, and is definitely worth updating to. Watch out for the news - it will only take a couple of days at most! This update will not change anything about the icon size, though.

0.93 will still take some time, it's release was tentatively set to 'autumn 2017'.