Free pen drive space extending software here helps extend an existing partition to unallocated space on the same disk, and detailed steps are shown here.

1. Free Software Extending Pen Drive Space
with Ease
Users may meet the situation: a newly bought 8G pen drive just shows 7G or less space
available. At this time, a piece of pen drive space extending software may help solve
the problem.
Why Available Space of Pen Drive Is Reduced
1G claimed by manufacturers equals to 1000MB while 1G in theory is 1024MB, so actual
size of pen drive is relatively smaller. Moreover, if some space on pen drive keeps
unallocated, its available space will be reduced, too. In general, unallocated space can not
be seen and used in Windows Explore but visible in Disk Management. Therefore, users
need to open Windows disk management utility to see whether there is such an
unallocated space on pen drive. If there is, extend the existing partition to it by using pen
drive space extending software (Windows can only recognize the first partition on
removable device, so there is always 1 partition on a pen drive).
Here, MiniTool Partition Wizard Free is highly recommended since it is free for all non
server users, safe enough to ensure data security, and easy to use. Next, let’s see how to
extend partition with this program.
--Source from
http://www.partitionwizard.com/resizepartition/pen-drive-space-extending-softwa
re.html
Extend Partition on Pen Drive with MiniTool
Partition Wizard
Firstly, run the pen drive space extending software and choose “Launch Application”
module to get its main interface shown below:

2. Then select the partition which needs extending and choose “Extend Partition” or
“Move/Resize Partition” from the left pane. Here, we choose the former to get the following
interface:

3. In this interface please take free space from unallocated space on the same drive to
extend the target partition. After that, drag sliding button to decide how much space to
take and click “OK” to go back to the main interface:

4. Now we can see the selected partition has been extended to unallocated space, so please
click “Apply” button to apply changes. Once the application is completed, we increase
partition size by using pen drive space extending software successfully.
If users are troubled by similar situations, try using MiniTool Partition Wizard to extend
partition on pen drive. For video help, please see Extend Partition.