There is indeed, but here are different definitions depending which country you are in and whether electrical wire or steel wire. Assuming you want the US data and for copper wire, the American Wire Gauge is appropriate. You can access the full table under Wikipedia 'American Wire Gauge'. Another entry is under 'Wire Gauge' which gives the history of various other definitions.
18 gauge electrical wire is 1 mm diameter, so will have cross section area 0.7855 sq mm, so 1 meter(1000mm) will be 785.5 cubic mm or 0.7855 cubic centimeters. The density of copper is about 8.9 g/cc, so 1 meter will weigh 7g. 1 ounce = 28 g, so 1 ounce of the wire will be 4 meters = 157.5 inches. Hope I have got the math right!