Citadel Death Toll?

Bioware, or rather Patrick Weekes, answered that question in 2012. No number is given as to how many perished, but a lot did survive.

100s of millions. It's always easy to crank up the narrative holocausts in stories for big effects and emotions, but once someone asks about the implications there is just cheap hand-waiving and appeasing ass-pulls.

I expect the whole death toll of the Reaper invasion to be in the trillions in total.  As for the Citadel I am like you I figured millions died.  I mean there were explosions in the arms of the Citadel.

Not on a space station though. Unless it's a hidden asteroid base or so.

I'd imagine at least hundreds of thousands, if not millions.

Any less, and it kind of removes the point of the direness of the ending's tone. Maybe its possible, but it would be dumb. If only some thousands had been lost by this point, I'd have preferred the game insert a section where we rally the inhabitants, since clearly the Reapers actually suck at this.
Yet, any more than it (several million, of the 100% of 13 million), and it wouldn't necessarily make sense as a place that the Reapers obtained very very recently and seem to be harvesting, not only mass slaughtering. We are given a sense that the Citadel's forces, whether C-Sec or civilian, could be able to hold out to a degree, and we can probably assume that its only been a maximum of days - not weeks, months - since the Citadel was moved to Earth.


Galaxy-wide, I think it depends. Yes, trillions of lives were at stake, but the point of the war effort and the Crucible was to save as many lives as possible, as soon as possible. 'Trillions' may be the total population of the known galaxy, but that could just amount to like, 2 trillion for all we know.
Its obvious that the death toll came to billions, likely many billions, whether from the initial attack, the war, or damages post-war. Post-war, the numbers might vary wildly. A low EMS Destroy could mean double the deaths for all we know, until they just maybe find a way one day to rebuild the network. A high EMS Control could mean very low deaths, as an intervening force and new tech ensures that so many more lives are preserved (under the Overlord Shepard). Synthesis might save the most lives - or it arguably ends them all, if you have the most negative viewpoint about it. I just assume that somewhere in the tens to hundreds of billions died, but that within decades of all endings besides Refuse and MAYBE post-low Destroy, something of a strong galaxy has at least started to recover.

Certain worlds are wrecks. Batarian territory would be largely gone, while the Turian home world would be riddled with disaster zones and ruined battlefields, but Earth would be somewhere in between - where most surviving structures and landmarks will be automatically tagged as historical sites. Colonies would range from untouched but weakened from the war economy, to utterly obliterated.

People can have their issues with Bioware painting such a bleak tone with ME3's original ending, contrasting to post-release 'wait wait it wasn't so bad' dev commentary, but I believe that in-universe the gist is that the galaxy got stabbed, was bleeding out, but the Crucible allowed extraction of the weapon while the patient/galaxy lies in stable (higher EMS) or critical (lowest Destroy EMS) condition. There's still a body/organic society to save. What's effectively true is that no life was untouched by the war in some significant way, but I don't even think the majority of the population died during the war or even the years after. If the Crucible failed, then we can go off dialogue that the war would have been largely turned in the direction of Reapers' victory in the coming months (max) no matter what, the galactic economy and probably other systems would have been basically eradicated within a year (or two max), and just the coming decade would remove at least almost all signs of desperate resistance and maybe even the very presence of any survivors. But as it was, its easy instead to imagine that post-war, a basic normalcy could be restored within months, most clean-up and recovery (besides long term demographical issues etc) would be made within years, and unless something goes really wrong (like I dunno, Reaper tech/controlled Reapers causing chaos, or whatever other dilemmas), the Reaper War's damage starts becomes living history after a decade, and starts dropping from living memory within decades further (notwithstanding long living species memories; maybe add more centuries eg. ME5 Liara teaser). The scale of the conflict does matter, but otherwise, it can be seen akin to the pain done to our world after the WW1-WW2 period; severe but recoverable.
Temporary (or especially permanent) loss of the relays would be terrible for so many, but I don't think we should write off the likely efforts of at least the fleet around Earth and its concentrated talent, in using any tech available to get something going again. We're given enough dialogue in the trilogy that the Council races (+ others really) COULD (and maybe are; ME5 could retcon some things in for sure) put resources into understanding the mass relays better enough to replicate them or even adapt new purposes, but governments and/or industry either didn't see the point, or maybe even suppressed such efforts so as to avoid another Rachni problem.
That is to say, the Citadel probably didn't lose several million, it was just bound to if the harvest continued without interruption. And the galaxy didn't lose trillions or maybe even hundreds of billions, just many many billions, and it was bound to lose everyone if the harvest continued without actually being stopped.

SwobyJ Really great detailed posts with a lot of info I did not know. I got the trillions figure from the fact that compared to the Asari, Turians, Salarians, Krogan's and Volus to name a few, humans are a young species. Many of the other species had thousands of years to explore space and colonize worlds before earth found the Prothean ruins on Mars. I had figured the total population was in the trillions. But I had forgotten to take into account the EMS scores and what will be the true canon ending. I just figured since the Reapers where attacking almost all over the milky way that the final death tolls would be staggering. Heh, if a high EMS score is the canon than the alliance of the milky way species did better than the Protheans and those who came before.

You make good points and bring up interesting topics like major cities being targeted first and the small towns being left for later.  Also I remember now Javik saying that the Prothean war with the Reapers took centuries.  It wasn't just one big invasion but several battles over the centuries.  I also forgot when I first said trillions that the current cycle won the war.  In the previous cycles the Reapers initially won and then the rest of the galaxy fell over time, and the civilizations were systematically erased. 

Hmmm..... death toll. Here's about how many humans were processed on Earth each day. Now listen to what Shepard says to Tali in London. A few months. I will assume few to be 3. For about 90 days the reapers have been harvesting Earth equaling to over 167 million dead. Let's stretch the few to be 4. That would be about 223 million dead. Nearly 2% of Earth's population. No idea how many dead on other planets. 

As I posted above, Bioware didn't give a number of deaths on the Citadel. Just said there were survivors. The Citadel houses about 13 million. I will assume about 2 million went there for refuge putting the total to 15 million. If I had to guess, I would say at least half were killed all from the crucible 

Clearly, many, many died. ME3 writers are just really saying that everything was so fast, and there's so many ways to be safe in (even temporarily) protected environments, that a post-ME3 recovery effort that focuses on rescuing Citadel survivors, would probably find a lot of them. Apparently up to millions. The Citadel is severely busted up, and the arms are breaking off/broken off, but it isn't shown as completely or even almost completely destroyed - even in the visuals of the original ending of Destroy, or low EMS EC Destroy.

Citadel aside, the galaxy was going to do a major recovery effort onto the Sol System anyway, whether the relays are quickly reestablished through the highest Space Magic, or it takes months or years to reach Earth and the allied fleet has to instead come together to ramshackle something of a very painful recovery in a meanwhile. Part of that initial recovery would mean reaching the Citadel's arms, within hours to days, and collecting as many survivors off the station as possible. Presumably, the station/arms don't crash onto Earth, so an effort is eventually made to rebuild the thing in the coming years to decades. And apparently, this station stays in the proximity to Earth, as shown in EC slides. Due to the collective effort of survivors of the war, both Earth and the Citadel may be seen as a joined capital of the new galaxy, as humanity ascends to at least the near top of governance, while also much more rapidly accepting alien (and potentially AI, up to including 'Reapers') presence and integration into its society.