Here’s a handy little conversion sheet. While you could use a calculator to figure out decimal equivalent for fractions of an inch, this is a bit quicker.
While some layout programs will allow you to work with fractions, I find it easier to work with decimal. Yet most printers I seem to work with always give me certain measurements in fractions. Thus the need for me to convert.
The conversion sheet is free, so grab it and keep it handy.