I have been using this little program for years, on and off anyway. I had lost it and asked a long time friend if he had a copy of it still. He located it online for me. If this little jewel doesn't have the calculations available that you need, which would be a slim chance, it offers a "custom" tab for you to set up your own calculations. I added it here in both ZIP and RAR files.
convert.zip
convert.rar
Just unzip it and save it to your desktop, or anywhere you would like. It's well under 600 kilobytes, as an executable file.
Some examples of what is available on this little program.