variable type char to variable type int

I'm trying to take a variable from type char to type int. I'm reading in the values as an array of characters, but these characters really represent numbers in hex. I can read in the string fine and print out the characters fine, I just can't seem to output the values as an integer. The strings vary between 2 bytes, 4 bytes and 28 bytes. So I need to be able convert each of these fairly quickly. Right now, I'm trying to set up an array with the different mulitplier values to use while converting, but is there an easier way?

There's some example code here... it might not be exactly what you want, but it's a start.

If it doesn't help, post what code you have and someone will help out.