Depth-of-Field Calculator

 This new calculator I found also calculates for the digital format, in addition to the regular 35mm film format.
If you're a non-techie, don't let the DOF lingo distract you...just fill in the four spaces, and press calculate. It will give you the closest point in focus, and the farthest point in focus, the 2 main things you're interested in.

Click here for DOF calculator forums