You lose a good amount due to formatting.
Windows Home Premium 64bit is around 20GB on its own.
Pagefile is as large as your physical RAM. May want to move it to a HDD.
If you haven't moved your user files, any downloads will go on the SSD.
You don't need a page file with 16GB of memory and you definately don't want it on an SSD f you use one. You also want to exclude your SSD from Defrag because it wears out the drive faster Configure this under Defrag schedule - Select disks. I only have 8GB of memory and my new build runs fine without a page file.
1) With 16 Gigs ram - Set page file max and min to 1024 mbs and leave on SSD.
Windows sets page file to 1.5 x ram - ouch.
2) Disable hibernation. Hibernation is not needed with SSD as boot times are fast.
Hibernation dot sys file is a hidden fill and can be upto size of Ram or 16 gigs - again Ouch
3) Manage or disable restore points. each restor point is about 300 mb and over time can consume a lot of space.