Apple - How to check whether my Intel-based Mac is 32-bit or 64-bit

Run this on the command line:

getconf LONG_BIT

This knowledge base article from Apple should provide you with the correct answer as it depends on how old your MacBook Pro is.

Basically if you have anything newer than an 2008 MacBook you have a 64 bit processor and OS…

Here is the cheat table

To tell if you are running the 32-bit or 64-bit kernel (which matters for some device drivers), launch System Profiler and click on the Software heading in the Contents section.

The line 64-bit Kernel and Extensions will say Yes if you are running the 64-bit kernel and No if you are running the 32-bit kernel.

Note: Mac OS X 10.6 Snow Leopard is the last release that a 32-bit Intel Mac can run, Mac OS X 10.7 Lion and up are, by default, 64-bit. Additionally, System Profiler was renamed to System Information in OS X 10.7.