LibreOffice calc Slow in Ubuntu Memory&Java

1.Increase memory
Open up LibreOffice Writer.
Click Tools -> Options.
Click Memory (under LibreOffice).
Increase the Graphics Cache -> Use for LibreOffice value (try 128 MB to start and increase further if needed).
Increase Memory per object (try 20MB to start).
Click OK.

2.One quite easy way to speed up LibreOffice (and OpenOffice) is disabling Java.

Go to Tools->Options, and then LibreOffice->Adnavced and untick the "Use a Java runtime environment"-option. This can make a huge difference in the speed of LibreOffice applications, but more special features might require Java to be enabled (in which case you'll get a popup asking if you wish to enable it again).

http://ubuntuforums.org/showthread.php?t=2237218
http://askubuntu.com/questions/109772/libreoffice-calc-goes-grey-takes-lots-of-cpu-cycles