So with a total of 21,000,000 that would be ever created this means a total of 6,603,174,603/21000000 = 314 bitcoin ratio against gold, so you can say per one bitcoin there is 314 gold ounces 
The units are completely arbitrary. You could also say that for every ounce of gold there are 320,000 satoshis, or that for every satoshi there are 2.7x1017 atoms of gold.