[Chris Hibner]

While my above post solves your math issue, you may have a bigger problem.

A continuous pot has a gap in which the wiper will not contact the resister band (right where it will flip from 5V to 0V). When that happens, the A/D pin will be at a floating voltage. You may get weird voltage readings in that band depending on how the A/D pin is "wired". Is there a pull-up or pull-down resistor on your board? If not, you should definitely add one so when the wiper loses contact, you have a defined voltage that is either 0V or 5V (not somewhere in between).