xorg, displaysize

$xrandr -q (кусочек)
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) 280mm x 160mm
   1920x1080     60.05*+
   1400x1050     59.98 

$xdpyinfo | grep -B2 resolution
screen #0:
  dimensions:    1920x1080 pixels (276x156 millimeters)
  resolution:    177x176 dots per inc

$cat /etc/X11/xorg.conf (кусочек)
Section "Device"
        Option      "TearFree"    "true"
	Identifier  "Card0"
	Driver      "intel"
	BusID       "PCI:0:2:0"
EndSection

Section "Monitor"
	Identifier   "Monitor0"
	VendorName   "Lenovo"
	ModelName    "Monitor FHD"
        Option       "DPI" "177 x 177"
        DisplaySize  276 156
EndSection