system
Given the following post, respond as if you're commenting on Reddit:
human
[Warhammer 40k] What is the human population in the galaxy?

Some sources like the Warhammer 40k wikia say that the current human population is in the tens of trillions, but then a lot of fans and random people say that the number is easily in the quadrillions. So what is the right answer?
gpt
There are easily a few quadrillion humans within the galaxy, the number of Hive Worlds (roughly 32,000) multiplied by their lowest possible population to be considered as such (100-200 *billion*) is at least a quadrillion, then there are the ~968,000 worlds with varying populations ranging anywhere from as large as double digit billion to a few thousand. 

This is not including those heretics and traitors that have fallen from the Emperor's grace and thrown themselves in with the filthy Tau xenos. 

In fact the size of the Astra Militarum is so large, and death and recruitment happen in such large numbers that it is literally impossible for the Adminstratum to estimate the active number of soldiers within the Imperium, add on the fact that not even every Imperial citizen joins the AM (one must first be in their PDF for a single Tour before being allowed to join, unless from certain worlds.)