Hi yeah bcos partitioning takes some space MBR or GPT
And now days win 8 takes even more there is some MB for recovery partition then EFi partition 100MB

for 1TB is 953,674 MB and windows output is 931 GB

here is good expl.

https://knowledge.seagate.com/articles/en_US/FAQ/172191en

Yes it has less size after formatting and it looks like your conversions from base 10 to base 2 are correct.

But before formatting, a 1TB drive will have more than 953GiB of total storage and more than 1TB of storage. After formatting it’ll have 1TB or 953GiB of storage.

The advertised storage of a hard drive is the storage space available after formatting.

A volume that has 1MB of storage, will have 1.048576MB of storage before formatting, according to the disclaimer on WD’s site. At least I think that is what they mean.

As used for storage capacity, one megabyte (MB) = one million bytes, one gigabyte (GB) = one billion bytes, and one terabyte (TB) = one trillion bytes. Total accessible capacity varies depending on operating environment. As used for buffer or cache, one megabyte (MB) = 1,048,576 bytes. As used for transfer rate or interface, megabyte per second (MB/s) = one million bytes per second, megabit per second (Mb/s) = one million bits per second, and gigabit per second (Gb/s) = one billion bits per second.

man what u askin ? that’s been decades that drives has less size after installing and formatting .. this is old school mate

Base10 Base2 Base10 Base2
36GB 34.3GB 160GB 152.6GB
40GB 38.1GB 200GB 190.7GB
73GB 69.6GB 250GB 238.4GB
80GB 76.3GB 300GB 286.1GB
100GB 95.4GB 500GB 476.8GB
120GB 114.4GB 750GB 715.3GB
146GB 139.2GB 1000GB 953.7GB

Defo there will be notice .. depend what u will be doing .. if u have only SATA II then u should buy cheapest msata or normal SATA II SSD tho