Hex Calculator Widget can do calculations in base 2, 10 and 16 with the most common features implemented. It has key bindings for most everything, and is designed to be a coder's calculator. It is based around a signed 32-bit integer.
What's new in Hex Calculator Widget
Version 1.5:
UI overhaul.
Updated the keybindings to use the command key instead of the ALT or option key (Sometimes the ALT key would fail to register).