You can convert Word documents in DOC format to ODF format using word-processors based on Open Document specifications, such as OpenOffice.org or LibreOffice. You might loose some specific formatting for Word documents in the process.
Convert Microsoft Word document (prior version 2007) to Open Document Interchange Format (ODIF).
We have found 2 software records in our database eligible for .doc to .odf file format conversion.
Apple macOS / Mac OS X software - convert doc to odf on OS X
A full-featured set of office applications for Mac OS X
Convert from doc 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 doc to odf. 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.
Multiplatform software - convert doc to odf on any platform
Full-featured word processing and desktop publishing tool from LibreOffice suite