Size of the Imperial military in 40K

[SpaceMarine93]

We all know that the total number of Space Marines in WH40K universe probably don't exceed beyond a few hundred thousand, but one thing I can never be certain about is the size of the other Imperial military forces. Can anyone give me a rough estimate on the size of the Imperial Guard forces? And the number of ships in the Imperial Navy?

[Srelex]

Numbers mentioned range from 'billions' to 'trillions'. Then again, IG strength is meant to fluctuate a lot, so there's no concrete number.

[Darth Tanner]

Space marine numbers are over 1,000,000 serving marines, not including space/vehicle crews which could easily double it.

The Imperial Guard are often called limitless and without knowing how populated the Imperium itself is it’s impossible to say how large it is. If we assume they have a military service level similar to War time America of around 8% then if for example there are a only a million worlds with average populations of 50 billion then you would have over 6 quadrillion in the PDF, Guard and Navy. Obviously that figure can go up a lot depending on how many planets are in the Imperium and how many of them are hive worlds. Also you have to consider that many worlds that are invaded draft everyone into fighting off the xenos hoards.

As for ships well a sector is roughly a hundred planets from the Gothic Sector example and a battle fleet usually comprises between 50-75 ships. On that basis there should be around 750,000 ships in the Sector battle fleets based on a million world Imperium. Again that would go up depending on the size of the Imperium and how many ships are not kept in the sector battle fleets. It would probably be safe to double that number to take into account all the ships kept in reserve groups and those engaged with keeping the Eye of Terror bottled up. That’s ships over a km in length, I don’t think they bother counting anything smaller in their fleet strengths.

[Serafina]

Keep in mind that sector battle fleets do not include the ships of the Adeptus Mechanicus, Adeptus Astartes, Adeptus Arbites and of the Inquisition and Rogue Traders.
It also doesn't include system defense ships - but those lack warp capability and are generally smaller than cruisers. Trade vessels are also often armed and are supposedly much more numerous than military vessels, but of course they don't match them in military capacities either.

[andrewgpaul]

There's also the mothballed ships and reserve fleets too, although I don't know how quickly they can rustle up crews for those.

[Ahriman238]

We all know that the total number of Space Marines in WH40K universe probably don't exceed beyond a few hundred thousand, but one thing I can never be certain about is the size of the other Imperial military forces. Can anyone give me a rough estimate on the size of the Imperial Guard forces? And the number of ships in the Imperial Navy?

Actually, its a million Space Marines, not counting support like pilots and techmarines, across a thousand chapters.

500 trillion is a number that gets thrown around a lot, thanks to an old 40k poster. There is some debate on whether that means 500 trillion men in the Guard, or if it is a rough population count for the entire Imperium. I tend to use that as my rough estimate though.

It may interest you to know that after the Stark Report, an estimate of the Tyranid threat, the High Lords of Terra approved a contingency plan of mass conscription that would use the IG as a cadre to train a force 5 times larger. Described as being equivalent to 'every man, woman and child in 3 Segmentum."

There's at least a couple million Sororitas. Billions of Skitarii.

I think Darth Tanner is alright on the numbers, though an Imperial Sector is a just a 200 ly cube, and can contain as few as 20 worlds. Also, for every 1 warship in the Sector and Segmentum Fleets, there are 9 other ships, freighters, tankers and troopships, mostly.

[Connor MacLeod]

We know the Imperium has millions of warp capable ships easily. We just dont know of what kinds and how many are warships. Space Fleet gave a rough idea that 90% of the Imperial Navy's fleets were transports and freighters and such (the Navy - or the Imperial fleet - controls all starships in the Imperium, barring some of the other indpendent organisations like the Space Marines or AdMech) and the other 10% were warships and private/civilian ships. I doubt there are more civilian/private ships than there are warships (civilian ships were supposed to be quite rare) so the bulk of that is probably navy ships. That meshes roughly with the BFG size of a battlefleets warship complement (50-75 warships in the game, hundreds in the BFG novels) Battlefleet Kornous expands on that and suggests a battlefleet comprises thousands of warships. In my opinion, the vast majority of ships either aren't true warships (the BFK thousands of ships reference could address that, eg armed merchant cruisers and such) or that the vast majority are stuck in mothballs - simply having huge numbers of ships does not mean you can effectively crew and maintain that number indefinitely (and even if you could, it probably would be needlessly expensive to maintain, even for the warlike Imperium.) The 50-75 ship complement represents "average" peacetime allocations, sort of the minimum they need to retain any sort of functionality at all. Depending on circumstances (eg outbreak of war or some other crisis) they might temporarily draw ships from the sector/segmentum reserves to bolter their fleet, replace losses, and the like.

It's also quite possible that the modern Imperium simply has far more escorts than it has capital ships - escorts are generally treated as expendable - quick and easy to build, but also comparatively more fragile than Cruisers and battleships (which take correspondingly longer to build but are also vastly more powerful/tougher.) Why this is we don't know, but its possible to spend decades, even centuries building cruisers (and anywhere from decades to millenia to build battleships. Of course, considering the size of some battleships, this isn't surprising.)

It's effectively impossible to know the true size of the Imperial guard because they dont know how many planets they accurately have (ranges anywhere from a million to billions), tithing is never centrally controlled but merely handled on an "as need" basis usually (and each sector/subsector has independent control of such) not to mention other issues like the possibiility warp time dilation in transporting them. The best you can do is estimate from annual tithing from the PDFs and even then that's imprecise (billions or trillions, depending on source and world and other variables.) The upper limit *potentially* is whatever percentage of the Imperium's population they can arm and equip and train. You could argue that they could grow into quadrillions, but that doesn't mean they can arm/equip or provide logistics for that number, so it's not very useful except AS an upper limit.

[KingDeath]

The number of warships within the Imperial Navy can be estimated if we keep in mind that each sector has between 50 and 75 warships of all sizes ( source BFG ) and between 100 ( Sabbat worlds ) and perhaps 200 planets ( rough estimate, the Calixis sector seems to get close to that number ). The Imperium has roughly a million worlds and thereore consists of between 5000 and 10000 individual sectors.

The lowest estimate would therefore been 250000 warships of all sizes for the Imperial navy while the highest rough estimate would be 750000 ships of all sizes. Ships which belong to inactive reserve fleets, astartes chapters ( perhaps 30000 ships? ), Mechanicus allies, Rogue Traders, Arbites cruisers, Ecclesiarchy ships as well as inquisitorial vessels and system defence ships, are of course not included into that number.

[Connor MacLeod]

It's actually 500-750,000 at least. BAttlefleet Koronus makes it explicit that there are thousands of sectors per segmentum minimum.. and that's conservative since segmentae are not all consistent in size. Indeed, Segemntum Ultima can make up 2-3 of the other segmentum in volume all by itself.