I have been having this problem with my laptop where the fonts seem too small. To fix this, I first had to check out my laptop's screen configurations:
Part of the output of this command is shown below. As can be seen it shows that my laptop screen is 'eDP1' and has dimensions of 290mm by 170mm.
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767 eDP1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 290mm x 170mm 1920x1080 60.05*+ 59.93 1680x1050 59.88
Another command that can find screen information is:
xdpyinfo| grep -B2 resolution
This command shows different screen dimensions. Its output is shown below:
screen #0: dimensions: 1920x1080 pixels (508x285 millimeters) resolution: 96x96 dots per inch
There is some discrepancy somewhere. To fix this, I had to create a monitor configuration file in /etc/X11/xorg.conf.d/90.monitor.conf that contained the correct screen dimensions. I got the screen dimensions by measuring them with a tape measure. The contents of the file are:
Section "Monitor" Identifier "eDP1" DisplaySize 290 170 EndSection
I then restarted i3 and my screen read comfortably. The output from the xdpyinfo command shows:
screen #0: dimensions: 1920x1080 pixels (290x170 millimeters) resolution: 168x161 dots per inch
I got most of the information to fix this here.