I would recommend downloading and evaluating a copy of VOLTS from Dolphins-Software @ www.dolphins-software.com.
The software can easily accommodate this calculation … and more!
The software requires the use of Microsoft DotNot Framework, which you must download and install first. I don’t believe that there are any conflicts with the use of the PC based software on a Mac.
To accommodate your inquiry with the use of the program you would simply enter the load, the cable or conductor type, conductor material type, the maximum voltage drop, the voltage parameters, ambient temperature and raceway type if applicable and the program will specify the conductors in accordance with IEEE Std 141 standards.