This is a simple Depth of field calculator optimized for the Nokia N900. The original script comes from this site but it was completely rewritten by me.
The script calculates the Depth of field for a given filmformat, focal length, f/No and object distance. The calculations can be done in meters and feet.
Read the Wikipedia article for more information about the calculations and depth of field in general.
The calculator is shown in an iframe below. The page can be saved as a single file so you can run it locally. Right click on this link and choose save as.