Calculating Surface Area of Compound

Is there any way to calculate the surface area of compounds such as **2,5-dimethylhexane** or **3-methylpentane**? If not, is there a database that has information on surface area of these compounds (**not polar surface area**). I'm doing an in-depth research between the correlation of surface area and boiling and melting point in branched chain isomers and really need to calculate the surface area of these branched chain isomers.


* if it's through a program, please specify if the program is free to use


