Motherboard Sizes - The Complete Guide

How to Choose a Motherboard Size

Ahead of giving you our top picks, we’ve broken down the key criteria for what to look for in a motherboard.

Just know that not all these factors will be important to you individually (many people don’t need to worry about having more than a few SATA ports, etc.).

Don’t be overwhelmed by all the factors, just focus on what’s important to you, and check out our recommendations if in doubt.

Form Factor / PC Case Size

Let’s start with an obvious one.

Whatever motherboard you pick, you want to make sure that you have an appropriately sized case to go with it (e.g. E-ATX case for an E-ATX motherboard).

Check out our joint-feature on PC case sizes if you want more info.

But in short, the type of motherboard you want will probably also guide the case size you need anyway (e.g. if you’re looking at a smaller motherboard, the case will have fewer hardware space/cooling options, but that’s the trade-off for portability).

CPU compatibility

Although not explicitly related to size, this one is worth covering as it’s one of the most important buying factors.

When purchasing a motherboard, make sure it’s compatible with the CPU you’re looking at.

Firstly there’s LGA vs PGA vs BGA.

There’s already good resource if you want the very technical explanation, but in short:

• LGA is most common for Intel CPUs.
• PGA is most common for AMD CPUs.
• BGA is more for manufacturers and not worth considering for your individual build.

Note: this isn’t universal, you may (rarely) in the future see an AMD CPU on LGA – but this will usually be very clear in a listing.

The most common socket types right now are LGA 1151 for Intel, and AM4 for AMD.

These will support the most common CPUs you’ll be looking at for gaming.

There will be more terms in this area that will probably confuse you like Z370 vs z390 (which is mainly just a difference in wifi/USB compatibility).

If you are confused here, don’t worry – just check the product listing!

We’ve only provided this info for the full picture. Once you’ve found the CPU you want, it’s pretty clear what a motherboard supports in the product listing like below:

PCI Slots

One of the big factors for a gaming computer.

The larger your motherboard size, the more PCI Express (PCIe) slots you will have available, these are what allow you to install graphics cards.

An E-ATX motherboard for example, will often have 4 PCI-e 3.0 slots, allowing for a 4-way GPU PC. 

Aside from GPUs, other PCI slots are often included if you have other focusses (e.g. installing a high-quality independent sound/network card).

Just know that you’ll usually have to put them in a place that blocks you from fitting an extra GPU.

That’s the beauty of a large motherboard though. Not many people need 4 GPUs, so those PCIe slots can come in handy for other things.

PCI-E x4 vs x8 vs x16

When looking at PCI-E slots you may notice the different numbers next to them (i.e. PCI-E 3.0 x4/x8/x16).

Putting it simply, a motherboard can only circulate a certain amount of data/bandwidth at a time.

So if you have a lot of PCI-e slots, some of them will be x4 – x8 which means they can’t output the same bandwidth as your main x16 slot/s.

But: There have been many benchmarks on what the performance difference is between these types.

The difference between PCIe x4, x8, and x16 is very minimal for performance/gaming.

We’re talking a couple of FPS in games.

This is because most GPUs don’t come close to actually requiring the x16 power that an x16 slot provides.

Whichever x type, you’re still going to be getting a majority of the card’s power overall.

SATA Ports

Larger boards will come with more SATA ports to allow you to connect more SSDs, HDDs and optical drives.

For most gaming builds, you’ll have more than enough SATA ports for your requirements on most boards.

It’s worth checking if you’re purchasing an mATX / mITX motherboard to ensure you have enough.

It’s only if you’re building say, a video editing PC, or if you have other requirements that means you want to install a lot of storage, should you be too worried about confirming these beforehand.

Miscellaneous

NVMe M.2 Storage

M.2 storage is less common than the standard 2.5″ SSD but worth your consideration if you’re all about speed.

It’s a type of solid-state drive that larger motherboards have become more compatible with over the last few years.

M.2 SSD vs SSD (2.5″) – An M.2 SSD installed via NVMe is around 5 times faster than a SATA-installed SSD.

Note that this is during benchmarking. In real terms to the user, this will likely be around 2-3 times faster.

These storage units are of course a lot more expensive (here’s our top pick) but run like a dream when you’re installing your OS and common apps on there.

If you like the sound of this, we recommend looking at an ATX or E-ATX motherboard.

You might be able to squeeze out the utility for an NVMe M.2 within mATX but it will likely mean the board is sacrificing bandwidth somewhere else.

Most motherboard listings will detail their support for this storage type so don’t fret about compatibility too much.

Just make sure to get an NVMe M.2 SSD (SATA ones perform similarly to a 2.5″ SSD) – here’s our top pick.

RAM slots

A majority of motherboards from E-ATX to Micro ATX will provide a minimum of 4 x DDR4 RAM slots.

The smallest form factor, mITX, tends to come with a maximum of 2 x DDR4 RAM slots.

In reality, this means you can still make a build with up to 32GB of storage which is plenty for gaming and most other functions.

Of course if you’re focussed on the best speed possible, more slots will help.

Not just because of the increased overall storage, but more RAM sticks are marginally more effective than overall storage (e.g. 4 x 8GB RAM is better than 2 x 16GB RAM for most users).

We wouldn’t worry about RAM compatibility too much unless you’re running some high-quality production/editing/streaming computer.

Gaming PCs won’t need more than 32GB for a while.

If you do have specialist requirements, high-end E-ATX/ATX motherboards include up to 8 RAM slots/256GB capability!

I/O Panel

The features available in an I/O panel will typically increase not just with chipset (which allows your mobo to support more inputs, e.g. USB 3.1 type C) but also the size.

E-ATX/high-end ATX motherboards often have a host of great ports available.

Smaller motherboards will usually have the standards though (some USB/audio ports) but check that your choice will have what you need, or you have a suitable extender.

Extra features

Finally, there are all the extra bells and whistles motherboards can come with.

The most common ones are:

• Integrated sound card
• Integrated network card (Wi-Fi/ethernet)
• Integrated Bluetooth (if not, adapters are dirt cheap)

Typically, larger motherboards include more of these features as it’s easier for the manufacturers to add.

We would say it’s often preferred to buy a standalone sound card or network card if you have PCIe slot room (not essential if your budget is tight, though).

Even Mini-ITX boards can come with these features integrated, just know that you may not get quite the same quality as large integrations or standalone cards.

That being said for smaller builds, we’d recommend getting integrated versions of features you need where possible so you’re not having to use your very finite USB/PCI inputs.