At least 16GB or larger. The process will erase all existing data.
Creating a bootable USB installer from a DMG file is a critical skill for Mac users looking to perform clean installations, downgrade operating systems, or repair machines that won't boot. Depending on whether you have access to a working Mac or are limited to a Windows PC, the process involves either Apple’s native terminal tools or specialized third-party software. Before starting, ensure you have the following: create mac os x bootable usb installer from dmg
This review looks at the reliability, speed, and usability of turning that DMG into a functional boot drive on a Mac. At least 16GB or larger
: Obtain the macOS installer from the Mac App Store or Apple's support pages. downgrade operating systems