What would the world population be if there had been no World War II and Holocaust?

That is hard to say.

It is difficult to estimate how all the people who did not survived WWII, and the Holocaust, would have effected the birth rate.

And don't forget that, despite its horrendous nature, the actual numbers of people who died was not that significant compared to the total world population. We refer to it as a World War, but there were significant populous areas that were barely affected by it all.

This site gives roughly 56 million deaths in the war.

http://www.hitler.org/ww2-deaths.html

Estimated world population in 1940 was around 2.3 billion.

https://en.wikipedia.org/wiki/World_population_estimates

That would make the death rate about 2 to 2.5% of the world's population at the time.

A scarey - and very sad - thought.

It would depend on the number of children produced who actually survived to adulthood and reproduced themselves, ie, birth rates today are dropping fast in more affluent countries today (Wikipedia) - some even have negative population growth - and in third world countries, infant mortality is still unacceptably very high. And then, what about plagues and so forth?

Now, back when I was in school, we were told of calculations estimating that, had the Holocaust never happened, there would be perhaps as many as 35 million Jews living in the world (as opposed to the 15 million who were around at the time). This was all a long time ago, and I can't remember where the sources got that estimate. But it only takes into account the Jews of the world who were affected by the genocide in Europe. So really it is still nearly impossible to give a decent estimate of what the world population would be. There might also not have been a baby boom in America had there been no war for the fathers of those children to come home from...