I remember have heard this long ago on Reddit but was never interested in doing the research needed, then I found it was indeed even more rarer 
Here is what I got:
"The World Gold Council estimates that all the gold ever mined totaled 187,200 metric tons in 2017" so this means there is a total equivalent in ounces of 187200000/0.02835 = 6,603,174,603 ever mined at this point in earth.
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
Links: https://en.wikipedia.org/wiki/Gold_reserve
Here is what I got:
"The World Gold Council estimates that all the gold ever mined totaled 187,200 metric tons in 2017" so this means there is a total equivalent in ounces of 187200000/0.02835 = 6,603,174,603 ever mined at this point in earth.
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
Links: https://en.wikipedia.org/wiki/Gold_reserve