Ratio of Antisemites to Jews in the world

World population: about 8.3 billion
Jewish population: about 15.8 million
Jews as a share of humanity: about 0.19% (roughly 1 in every 525 people is Jewish).

Surveys such as those conducted by organizations like the ADL have found that roughly 20–45% of adults in different countries endorse multiple antisemitic stereotypes, with the global average often estimated around 25–30%. This does not necessarily mean those people actively hate Jews; it indicates they hold several prejudicial beliefs.

If we use a 30% estimate:

30% of 8.3 billion ≈ 2.5 billion people holding significant antisemitic attitudes.
Compared with about 15.8 million Jews, that works out to roughly:

2.5 billion : 15.8 million ≈ 158 : 1