Most DSP software allows you to input time delay numbers in either actual distance measurements or in milliseconds, but regardless, you still have to eventually break out a measuring tape to come up with the numbers. @ErinH has a site that does the conversion for you;
http://tracerite.com/calc.html
Like I mentioned earlier, figure out which driver(s) are the furthest from you ears and make them the reference (don't apply T/A to them)... then align all other sources by applying T/A.
Remember that T/A should be done after gains, crossovers and RTA's have been done as a fine tuning of the sound stage. The pinned threads from this link are some good sources for the initial setup steps;
https://www.diymobileaudio.com/forum...our-members.5/