Khan Academy
Khan Academy: Hexadecimal Numbers
Practice converting hexadecimal numbers to binary and decimal numbers, in this set of practice questions designed for AP Computer Science Principles students.
University of Illinois
University of Illinois: Mste: The Binary Calculator Applet
The binary number system is used to represent data in digital form. This site provides a binary calculator that will convert between binary, octal, decimal and hexadecimal, perform simple addition and subtraction, and do compliment and...