This may seem a bit strange, but by default the Raspberry Pi only uses as much of the SD card as the operating system requires. This means that even though you might have used a large SD card, the operating system won't use it.
To fix this so that all the space on the SD card can be used, use up / down cursor keys to
select the 'expand_rootfs' menu option and hit return.
Once you do that, there will be some screen flashing as a script is run and then you will see
the following confirmation.
Press Return again to
return to the main menu.
This guide was first published on Dec 04, 2012. It was last
updated on Oct 17, 2018.
This page (Using the Whole SD Card) was last updated on May 04, 2015.