Microsoft has also stated this as the minimum system requirements!.
Hard drive size:
32GB or larger hard disk Note: See below under “More information on hard drive space to install or update Windows 10” for more details.
https://www.microsoft.com/en-US/windows/windows-10-specifications#sysreqs
But if you read those Microsoft's system requirements for 10, you will find that if you only go on them you will be sadly disappointed in performance.
For reasonable performance should have at least:
2 gigahertz (GHz) or faster processor.
4 gigabyte (GB) of RAM for 32-bit or 8 GB for 64-bit
500GB hard drive
DirectX 9 or later with WDDM 1.0 driver
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