Both RAR and TAR are compressed archives and hence can be re-packed between each other. The easiest way is to use a program that supports both of these formats, because that will speed it up considerably. The alternative would be to use one software to decompress .rar files and another to compress to .tar format.
Convert WinRAR RAR compressed archive to Unix standard Archive format, Tape Archive.
We found 6 software records in the database related to .rar to .tar file format conversion.
Microsoft Windows software - convert rar to tar on Windows
Popular open source file archiver with a high compression ratio
Convert from rar file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned rar to tar. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
One of the many available file compression utilities
One of the oldest and most popular shareware file archiver and data compression utility
Freeware file compression tool
Apple macOS / Mac OS X software - convert rar to tar on OS X
A compression utility for OS X
A compression utility for Mac