Minimum size for a /home partition?

Minimum size for a /home partition?

Here's how my partitions are currently set up:
500 GB HDD: [21 GB Free Space] [145 GB Windows partition - unfortunately I
can't move it so it starts at the beginning of the Hard disk] [175 GB Data
partition]* [145 GB Extended partition, containing / and Swap]
SDD: [30 GB used as a cache for the HDD in Windows]
*Note that my "My Documents." "My Downloads," etc. folders are relocaed to
the data partition. The "Documents," "Downloads," etc. folders in linux
are symlinked to the same folders.



I'd like to reinstall Ubuntu and put / on the SSD. I'd also like to make
use of the 21 GB on my HDD before the windows partition. Here's what I was
thinking:
HDD: [8 GB SWAP] [13 GB /home]** [145 GB Windoze] [320 GB Data]
SDD: [30 GB / ]
**Alternatively, I could make this 21 GB and move the SWAP partition to be
after the Windows Partition.



My question is: What's the minimum size I can make my /home partition so I
will probably never run out of space, given that all of my Documents,
Downloads, and Media will be on a seperate partition?