Comment 2 for bug 506538

    If you know ahead of time what the units are, then the best thing to do is choose manual scaling instead of automatic. If you choose a manual scale factor of 1 then the program will convert from mm to pixels. If you choose a scale factor of 10 then the program will convert from cm to pixels. The output is multiplied by the scale factor when doing the conversion.
    Could you try this and see if it helps?