Hi, I followed https://wiki.archlinux.org/index.php/Xorg#Display_size_and_DPI . I measured the screen size of the LCD and the CRT manually and in addition I calculated the screen size of the LCD. FWIW manual measuring provided the same result as the calculation. This is my xorg.conf [rocketmouse@archlinux ~]$ cat /etc/X11/xorg.conf Section "Monitor" Identifier "HDMI2" DisplaySize 526 296 Option "PreferredMode" "1920x1080" Option "Primary" "true" EndSection Section "Monitor" Identifier "VGA1" DisplaySize 367 278 Modeline "1024x768" 65.00 1024 1048 1184 1344 768 771 777 806 Option "PreferredMode" "1024x768" Option "RightOf" "HDMI2" EndSection Section "Device" Identifier "Card0" Driver "intel" #Driver "vesa" EndSection Section "ServerFlags" Option "BlankTime" "0" Option "StandbyTime" "0" Option "SuspendTime" "0" Option "OffTime" "0" EndSection For my session I added a few modes using xrandr: [rocketmouse@archlinux ~]$ xrandr Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767 HDMI1 disconnected primary (normal left inverted right x axis y axis) HDMI2 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 530mm x 300mm 1920x1080 60.00*+ 50.00 59.94 1920x1080i 60.00 50.00 59.94 1680x1050 59.88 1600x900 60.00 1280x1024 60.02 1280x800 59.91 1280x720 60.00 50.00 59.94 1024x768 60.00 800x600 60.32 720x576 50.00 720x576i 50.00 720x480 60.00 59.94 720x480i 60.00 59.94 640x480 60.00 59.94 720x400 70.08 VGA1 connected (normal left inverted right x axis y axis) 1024x768 60.00 + 60.00 800x600 60.32 56.25 848x480 60.00 640x480 59.94 1152x864_90hz_xdh_default 90.00 1440x960_86hz_xdh_music-1 86.00 1368x768_90hz_xdh_music-2 90.00 1024x768_60hz_xdh_no-risk 60.00 VIRTUAL1 disconnected (normal left inverted right x axis y axis) [rocketmouse@archlinux ~]$ xdpyinfo | grep "screen" -A2 # HDMI LCD on and VGA CRT off default screen number: 0 number of screens: 1 screen #0: dimensions: 1920x1080 pixels (506x285 millimeters) resolution: 96x96 dots per inch [rocketmouse@archlinux ~]$ xdpyinfo | grep "screen" -A2 # HDMI LCD off and VGA CRT 1024x768 default screen number: 0 number of screens: 1 screen #0: dimensions: 1024x768 pixels (269x201 millimeters) resolution: 97x97 dots per inch [rocketmouse@archlinux ~]$ xdpyinfo | grep "screen" -A2 # HDMI LCD off and VGA CRT 1152x864 default screen number: 0 number of screens: 1 screen #0: dimensions: 1152x864 pixels (301x226 millimeters) resolution: 97x97 dots per inch Is this a bug or do I misunderstand something? Regards, Ralf