Mike, Here is a table I made for that: wire gauge Ohms/1000 ft. turns/inch 10 1.040 10.0 12 1.650 12.0 14 2.630 15.0 16 4.180 19.0 18 6.640 23.0 19 8.051 27.8 20 10.500 29.0 22 16.900 37.0 24 26.700 46.0 There is of course different enamel thicknesses from different manufacturers, but this should give you a very close approximation(should be within a turn or two over the entire coil) Hope this helps, Mike