Method One:
For: Eclipse
After opening Eclipse: Help-->about eclipse-->installation details-->configuration
If you see the x86 word that Eclipse is 32bit, and if you see x86_64 or x64, Eclipse is 64bit.
For: MyEclipse
After opening myeclipse: Help-->about myeclipse Enterprise workbench-->installation details-->configuration
If you see the x86 word description MyEclipse is 32bit, conversely, if you see x86_64 or x64 words that MyEclipse is 64bit
Method Two:
For: Eclipse
Open the Eclipse.ini file in the Eclipse installation directory with Notepad
If the value set by Launcher.library is written in X86, it means that Eclipse is 32bit, and if x86_64 or x64 is written, Eclipse is 64bit, as
For: MyEclipse
Open the Myeclipse.ini file in the MyEclipse installation directory with Notepad
If the value set by the Launcher.library is written in X86, the MyEclipse is 32bit, and if the x86_64 or x64 is written, MyEclipse is 64bit.