Bethesda have released the system requirements for Fallout 4 on PC along with some other information to do with the release.
PC Systems Requirements (Requires Internet Connection and Free Steam Account to Activate):
Minimum
Windows 7/8/10 (64-bit OS required)
Intel Core i5-2300 2.8 GHz/AMD Phenom II X4 945 3.0 GHz or equivalent
8 GB RAM
30 GB free HDD space
NVIDIA GTX 550 Ti 2GB/AMD Radeon HD 7870 2GB or equivalent
Recommended
Windows 7/8/10 (64-bit OS required)
Intel Core i7 4790 3.6 GHz/AMD FX-9590 4.7 GHz or equivalent
8 GB RAM
30 GB free HDD space
NVIDIA GTX 780 3GB/AMD Radeon R9 290X 4GB or equivalent
Additionally Bethesda have confirmed that the console versions will require 28-35GB of space, depending on territory and languages supported.
Bethesda also made not that Fallout 4 will become digitally available at 12:01am on November 10 (in North America it's 12:01 am EST).