Unit Scout understands calculations stated in terms of unit expressions (such as '100psi*ft^2') and converts them into SI units per default or every other unit specified by the user. No user interface is required. The program can be controlled from everywhere - editor, browser, and spreadsheet. Unit Scout is customizable with user defined units simply stored in a CSV file. Conversion requests and results are logged in a journal file. Currency factors are always up to date as they can be polled from Google. Unit Scout is free of charge.
Download and use it now: Unit Scout