Tank calculations?

[MikeP]

It's a possibility that I may get my dads old fish tank (which is very exciting for me). I would like to know how many gallons it is. Does anyone know how to calculate gallons by the tank dimentions? It is 60 inches long 30 inches tall and 24 inches deep. So it's pretty big. I estimate I can fit at least 4 tanks the size of of my 55 gal in it. Also how much would a tank this size wiegh? I'd hate to have it end up in my basement. And one last thing, it is kinda old (at least 15 years) is there anything I should consider when filling/maintaining an older tank that size. It has not had water in it for many years either.

Thanks for any help.