...Wait a moment!
I've just seen I can add attachment to any post... so I can add my tool just here:
It's a file in Excel (.xls) standard format so - I think - you can open it with any spreadsheet program.
The file is zipped: you must extract it before you can open it.
It has several uses:
1) it converts a size from one scale to another (if you want to rescale a part)
2) it calculates the percentage of shrinking if you want to print in a smaller scale or enlargement if you want to print in a bigger scale
3) it calculates your customized part dimension if you know the dimension of the real object
I hope it can help you saving your remaining brain cells... it worked for me! (...partially...
)