I will setup a USB key to install Mavericks.
I would like to know the needed size of the partition to install Mavericks.
For me, the Mavericks partition uses 5.36 GB (5,355,311,104 Bytes) (per Disk Utility). That's 4.98 GB in old-school "binary" types like me (4.98 GiB).
This is subject to change given partition overhead, block size, a Mavericks version. So I'd allocate a little more to the partition.
The Mavericks install app is about 5.3GB and it is compressed. That should be how much space it will take up on a USB stick. Just drop the installer on the stick and double click on the installer to install.
I have partitioned my 64 GB USB stick into two parts, one being 5 361 369 088 b large out of which 5 951 488 b is free after making it Mavericks installation disk.