For a live-only pendrive and a persistent live pendrive 4 GB is enough. But you may want at least 8 GB (better a fast USB 3 pendrive with 16 GB) for a persistent live drive.
For an installed system at least 8 GB is necessary for testing. For real usage you need at least 16 GB (space to install application programs and data files). And it makes a real difference to have a fast USB 3 pendrive. Otherwise the installed system will be slow.
@Filiberto,
For a live-only pendrive and a persistent live pendrive 4 GB is enough. But you may want at least 8 GB (better a fast USB 3 pendrive with 16 GB) for a persistent live drive.
For an installed system at least 8 GB is necessary for testing. For real usage you need at least 16 GB (space to install application programs and data files). And it makes a real difference to have a fast USB 3 pendrive. Otherwise the installed system will be slow.
See this link,
https:/ /help.ubuntu. com/community/ Installation/ FromUSBStick# Prerequisites