SFF Philosophy: What counts, what matters?


Jessica. Wayward SFF.n Founder
Silver Supporter
Feb 22, 2015
For me I am not interested in SFF but more space efficiency. If someone came up to me and showed me a quad SLI 22 core x99 setup with 10tb of ssd and another 20tb in hard drives, and it stays under 60C no matter what (OK doesn't need to do all of this but you get the point) but is 60L, that's just as impressive as any SFF build.

Doing that in 60L is easy, 35-30L would be more impressive. If you really, really tried I think it's even possible in a Cerberus-X at 22L, though the 60C part might be a bit difficult :D

But I agree with the sentiment, a packed 25L case is more impressive to me than a 10 liter case that's mostly empty.


SFF Lingo Aficionado
Apr 18, 2016
When I first realized that I was an SFF enthusiast I was eye-balling a Silverstone case, more specifically the RVZ02. With this said, I really wanted something that similar in size to a console. I wondered why there wasn't much on the market that appealed to high-end SFF machines, and I got the idea that if a console could be small and somewhat powerful why not a PC? My philosophy, or really my hopes would be that we as a community can continue to pack higher end hardware into machines, maybe even to the point where 4K and 100+ FPS becomes the norm even for us. Lol

I believe and agree with the statements that a SFF PC should fit the owner's needs, whether it's to be a simple HTPC or a high-end gaming machine. I also believe in a bit of minimalism, not more than what you need...but everyone's needs/wants are different; for me it's just a PC the size of a console that can push 60+ FPS at 1080p and I'm happy. Besides this things like PSU's, Videocards, and just about any other component are elements that should be taken into consideration for being minimalistic. Ever since I've been a part of this community I have seen many forum members do absolutely amazing things within a small amount of space, from things like water-cooling, or cramming components into a sub 5 liter chassis. The things done and posted here is just evidence that shows how far we can push space efficiency, as well as how far people are willing to go with their hardware and passion for SFF.

I really enjoyed reading everyone's varying philosophies on SFF, and I hope this thread in particular sheds more enlightenment to all of us. :)
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Cramming big things in small boxes since 2006
Jul 2, 2015
Ah, the old "What defines SFF debate..." It's something that's quite personal to me. I know it's something I've even talked about in the old Mod Brothers and Losias podcasts. For me, it's always been more about the amount of hardware that will fit in a given space. For example, putting a Rpi in a S4 certainly wouldn't count as SFF in my eyes. SFF must make the most of any and all usable space inside a case, while still not compromising performance. I was able to put that into physical form with my Project: Rogue mod. It took a 43l NZXT Rogue, which was a massive mATX case, and made it decidedly SFF.

It was modified to fit a ATX motherboard, and a few other components. Namely, 2 power supplies (1200w NZXT and a 600w 24v Meanwell). Dual 240mm radiators, pump, reservoir, Wintsch Labs Peltier CPU block, five 3.5" hard drives, dual slot load optical drives, a pair of Dakota Digital automotive gauges, 10.1" display, 5.25" Matrix orbital display, Belkin PowerMate, a secondary picoITX system and 2.5" hard drive, integrated fan controller, and six 120mm San Ace fans. Whew... It was capable of sustaining -23C CPU temps under load. It was solely responsible for heating the bedroom of my house, and when those San Ace 1011's spun up at full speed, it was like running a vacuum. It also happened to weigh almost 90 pounds. So, SFF? Most definitely. ;)



Shrink Ray Wielder
Feb 22, 2015
Reviving this thread because the question of "what is SFF?" has come up again, and mods are loathe to let a new thread be spawned on that topic. So, for those who might want to discuss the question, this seems like an appropriate place.

19 or 20 liters is a totally arbitrary number, and in my view should only serve as a rough guideline for "this is around where the SFF definition should start/end." But certainly, cases above that can still be quite compact, relatively speaking, and can appeal to people for the same reasons the smaller SFF cases do (portability, footprint, spatial efficiency, etc.) The Cerberus X, for example, is a little over 20L, yet most people here still consider it SFF, and relative to other 40L+ ATX cases, it's certainly much smaller.

So to me it doesn't make much sense to take a hard line stance against a case "belonging" on this or any other forum/thread because it doesn't qualify under the arbitrary 20L> definition. If a case is in the spirit of SFF, then it does a disservice to bar it from discussion. Now obviously, whether something is "in the spirit" of SFF is a subjective evaluation, but I would tend to err on the side of allowance up until the point where most people would agree that it clearly isn't.


Shrink Ray Wielder
Jan 25, 2018
I suppose anyone can have his own definition of SFF. Personally, I do not consider so-called 'space efficiency' as part of the definition. (BTW, for those who consider this as the determining factor, would you explain how does one measure this efficiency? Does one just add up the volumes of all individual components and then the sum is divided by the volume of the chassis to arrive at a quotient? And then, how close to 1.0 is it considered SFF?)

Some years ago I had a huge Alienware full tower stuffed with all bells and whistles (RGB, watercooling...etc) and there is no way that I would dare to call it SFF. If that were SFF, I would not have come to this forum. Also, I consider moving the power supply unit outside of the case is a 'compromise'. (I do not mean to offend anyone)

When I first came here, I was told that 19L (or 20L? I do not remember) is used by Intel to designate SFF. I dug a little deeper and it turns out that Intel actually follows the definition of IDC (International Data Corp in the US, which I have never heard of). Basically, according to them, 8-19 litre chassis is SFF and 4-8 litre chassis is Ultra SFF (uSFF).

Note that this is just the volume of the chassis. It does not address the situation when a component (eg the power supply unit, or a watercooling radiator) is put outside or installed/attached to the chassis externally.

Anyway, I have an interesting question for the community here. Do you consider a build with an Open Benchtable Mini, which measures 190(L) x 230(W) x 78(H), a SFF?
Eg https://uk.pcpartpicker.com/b/HrpG3C
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Maker of Awesome | User 1615
Platinum Supporter
Mar 6, 2017
In regard to that thread, I had a response typed up before it got locked, essentially encouraging discussion in pre-existing threads and, should ever a communal consensus occur, in the feedback subforum. Though a discussion that large would likely be noted before that was necessary.

Personally I do favor the < 20L definition and considering the size of Cerberus X I was surprised the forum goes by 19L or less. I also tend to include the volume of external power units due to the need to transport them with the case, and exclude things like case-feet and gpu-flanges when determining the bounding box. "Space Efficiency Factor" is something I only really consider in cases > 20L. Generally yeah, that's based on case volume divided by component volume.

I also liked the old system of having larger builds in "Off-Topic." Seemed pertinent to keeping the forum orderly.


Lord of the Boards
SFFn Staff
May 9, 2015
I think my Cerberus X is not SFF because it only has a single small GPU inside and is basically 50% empty. Multi-GPU is so 2016 apparently.
If I go to a LAN party though, it's definitely SFF with those 60-80L behemoth cases with lower specs than the 21L Cerberus X.

It depends on what you expect from it. I like SFF because of the challenge and there is no challenge in a large case with a lot of room for everything. So I like to think my stuffed Ncase M1 was a lot more SFF than my current lofty Cerberus X.
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Shrink Ray Wielder
SFFn Staff
Nov 14, 2017
Honestly, sff for me is under 7L with NO external brick for itx, and 20L for matx


Chief Procrastination Officer
SFFn Staff
Jun 29, 2015
I dug a little deeper and it turns out that Intel actually follows the definition of IDC (International Data Corp in the US, which I have never heard of). Basically, according to them, 8-19 litre chassis is SFF and 4-8 litre chassis is Ultra SFF (uSFF).

This is what I tend to apply, this replaces the old "tower" denominations:

Tower cases are often categorized as mini-tower, midi-tower, mid-tower or full-tower. The terms are subjective and inconsistently defined by different manufacturers.

Full tower cases are typically 56 cm (22 in) or more in height and intended to stand on the floor. They can have anywhere from six to ten externally accessible drive bays, although in recent years (as of 2018), this has shifted to offering better airflow in the front by moving the drive bays elsewhere in the case. The ratio of external to internal bays is shifting, however, as computing technology moves from floppy disks and CD-ROMs to large capacity hard drives, USB flash drives, and network-based solutions. The full tower case was developed to house file servers which would typically be tasked with serving data from expensive CD-ROM databases which held more data than the hard drives commonly available, but are moving now towards being showpiece display cases with custom water cooling, lighting, and tempered glass (replacing acrylic). Hence many full tower cases include locking doors and other physical security features to prevent theft of the discs. This is a high-end case intended for desktop systems and doesn't include security features.

Mid-tower cases are smaller, about 46 cm (18 in) high with two to four external bays.

A mini-tower case will typically have only one or two external bays.[2]

source: wikipedia

People likes to categorise everything, this is why we end up with a song tagged as "Progressive Neo Rock Gring Core Acoustic Country". With bounding volumes, this gives a rough idea of how big the case might be, without knowing the exact dimensions. This makes listing chassis on webstore easier for example.

Now, space efficiency is another thing.

A chassis might be big but efficient spacewise...

(above is a Supermicro blade that takes 4x Xeon E5-2600 v4 .... it is a lil over 6 litres)

...or small and full of air...

(above monstrosity .... it is a lil over 12 litres)

About external power bricks ... this is a topic of perpetual disagreements. I personally like them but I am also in favour of accounting them into the chassis overall volume. While you have to carry them in addition to the chassis by itself when you move, they offer more flexibility when designing the chassis.

The PSU is something that takes a large amount of the chassis internal volume and you have to manage unused cables and/or long ones (unless you run full modular or custom size cables). With an external brick, you can achieve narrower, shorter and/or less tall chassis. You do not have to sacrifice front intake because this is the only place where the PSU can be put without increasing chassis size.

For me, SFF is context dependant. For an end-user (1 CPU, 1 GPU and an SSD), I'll consider that uSFF is the only SFF. Professionals might want to go a little bigger for extra storage or more expansion cards (mATX/ATX). For servers and HPE, only the density matters (blade servers for example).