The iso is about 4.7GB. After installing it to disk and running windows updates it occupies about 20GB.

How much space does a Windows 7 install take?

1 gigabyte (GB) RAM (32-bit) or 2 GB RAM (64-bit) 16 GB available hard disk space (32-bit) or 20 GB (64-bit)

How many GB is Windows install?

A fresh install of Windows 10 takes up about 15 GB of storage space. Most of that is made up of system and reserved files while 1 GB is taken up by default apps and games that come with Windows 10.