You may download my Binary/Decimal/Hexadecimal Converter and Bit Counting tool Registerer from Bintray. The tool is currently available for Max OS X (Intel), Windows and Linux (Beta). An Android version may be coming on request.
Main article: Easily Counting Bits for Registers
Downloads: 
Downloading via Chrome may bring a ‘malicious’ warning. This is a false positive and you may check this via VirusTotal or similar service.
Full source code is available on GitHub: https://github.com/MikeBergmann/Registerer