Here are the steps you need to add a new custom resolution and apply it. Following steps are for adding a 1920x1080 resolution, but you can use it for any other resolution you want. But make sure your monitor and onboard graphics support that resolution.
# First we need to get the modeline string for xrandr # Luckily, the tool "gtf" will help you calculate it. # All you have to do is to pass the resolution & the- # refresh-rate as the command parameters: gtf 1920 1080 60 # In this case, the horizontal resolution is 1920px the # vertical resolution is 1080px & refresh-rate is 60Hz. # IMPORTANT: BE SURE THE MONITOR SUPPORTS THE RESOLUTION # Typically, it outputs a line starting with "Modeline" # e.g. "1920x1080_60.00" 172.80 1920 2040 2248 2576 1080 1081 1084 1118 -HSync +Vsync # Copy this entire string (except for the starting "Modeline") # Now, use "xrandr" to make the system recognize a new # display mode. Pass the copied string as the parameter # to the --newmode option: xrandr --newmode "1920x1080_60.00" 172.80 1920 2040 2248 2576 1080 1081 1084 1118 -HSync +Vsync # Well, the string within the quotes is the nick/alias # of the display mode - you can as well pass something # as "MyAwesomeHDResolution". But, careful! :-| # Then all you have to do is to add the new mode to the # display you want to apply, like this: xrandr --addmode VGA1 "1920x1080_60.00" # VGA1 is the display name, it might differ for you. # Run "xrandr" without any parameters to be sure. # The last parameter is the mode-alias/name which # you've set in the previous command (--newmode) # It should add the new mode to the display & apply it. # Usually unlikely, but if it doesn't apply automatically # then force it with this command: xrandr --output VGA1 --mode "1920x1080_60.00"
Original source: https://gist.github.com/debloper/2793261
I also wrote a script that does all these steps automatically. You can try it out if the above steps seem too complicated for you: https://gist.github.com/chirag64/7853413