Best Web Design Quote Calculator?

I've been doing freelance web design for a few years, and I'm trying to get a better idea for pricing. That's always the hardest part for me. I'm curious how you all determine pricing when giving a quote? I'd like to create an automated quote calculator, though it would only be an estimator really since there's generally some variables that are hard to quantify. A calculator would at least be a good place to start.
Does anyone have any suggestions for online quote calculators, or just some general advice as far as that goes? Thank you for any suggestions!

Here's a pretty decent tool to help with project estimates:
http://estimator.astuteo.com/

I've been using this for a few months now.

Just do what that link does, put out every step you think there will be and time each of those by your hourly rate. I generally add a bit to that to account for things happening (which they normally do).