Mini ITX build guide: planning a small form factor PC

How do you plan a mini ITX build?

Plan a mini ITX build around the case, not around the parts you would like to have. In a mid tower nearly everything fits, so you can choose the parts first and the case last. In a small form factor PC the order is reversed: the case sets hard limits, measured in mm, on the graphics card, the cooler and the power supply, and every other choice has to live inside them. Open the specification of the case you like and write down its limits before you look at anything else. Then work through the checklist below in order. Each line is covered in more detail in the sections that follow, and the configurator will flag the main conflicts for you as you add parts.

• Case: its volume, and which motherboard and power supply formats it accepts
• Graphics card: maximum length, thickness in slots, and height
• Cooler: maximum height, or the radiator sizes the case can mount
• Power supply: SFX, SFX-L or ATX, and how long it may be
• Motherboard: mini ITX, with two memory slots and one PCIe slot
• Airflow: where air comes in, where it leaves, and which fans fit

How do you know if a graphics card fits in an ITX case?

A graphics card fits when it clears three limits in the case specification: length, thickness and height. Length is the one everyone checks, and it is listed as the maximum graphics card length. Thickness is counted in expansion slots. Many small cases take two or at most three slots, while the large coolers on upper-class cards can be thicker than that. Height is the dimension people forget: a card that stands taller than its slot bracket, plus the power cable plugged into its top edge, can press against the side panel. Leave a few mm spare in every direction, because cables need room to bend. If you want a strong card in a very small case, look at the compact two-fan versions of a model before the largest three-fan ones.

What CPU cooler fits in a mini ITX case?

The cooler that fits is one below the maximum cooler height in the case specification, and in small cases that number can be very low. Slim cases that place the graphics card behind the motherboard often leave room only for a low-profile cooler, while taller cases accept a regular tower cooler or a liquid cooler. A liquid cooler needs a mount for its radiator size, so check which sizes the case lists and where they go. Choosing a processor that runs cool makes all of this easier: the Ryzen 5 9600X and Ryzen 7 9700X are both rated at 65 W TDP, which a compact cooler handles far more quietly than a high-wattage chip. Also check that a wide cooler does not overhang the memory slots on such a small board.

Do you need an SFX power supply for a mini ITX build?

You need whichever format the case is built for, and in the smallest cases that is SFX. An SFX power supply is much smaller than a standard ATX unit. SFX-L has the same width and height but is longer, which leaves room for a larger fan. Some bigger ITX cases accept a normal ATX power supply, usually with a limit on its length. Whatever the format, check the connector: cards from the RTX 5070 upward use the 12V-2x6 (16-pin) plug, and an ATX 3.1 power supply carries that cable natively. Choose a fully modular unit so that you install only the cables you use, because spare cables have nowhere to hide in a small case. 80 PLUS Gold is the sensible efficiency class, and less waste heat is welcome in a tight space.

What are the limits of a mini ITX motherboard?

A mini ITX motherboard measures 170 by 170 mm, and that small area costs you slots, not speed. You get two memory slots instead of four and a single PCIe x16 slot, which the graphics card takes. That leaves no room for a sound card or capture card later, so choose a board with the features you need, such as Wi-Fi, already built in. With only two memory slots, buy the full amount of memory as a matched pair from the start, because adding more later means replacing the modules you have. Storage is tighter too: expect one or two M.2 slots, with the second often on the back of the board, and fewer SATA ports and fan headers than on an ATX board. The socket and memory type rules are the same as for any other size.

Does a small case run hotter or cost you FPS?

A small case does not cost you FPS as long as the parts stay within their temperature limits, because the frame rate is set by the processor and the graphics card, not by the box around them. The table below makes the point with figures estimated by our FPS model: the same pair gets the same result in either case, and the model does not take the case into account at all. What a small case changes is how hard the fans work. Less air and tighter gaps mean higher temperatures or more noise for the same parts, and a part that overheats slows itself down. So give the case a clear airflow path with both intake and exhaust, choose parts with modest power draw where you can, and expect to spend some time tuning fan speeds.

What does the compatibility check cover for a small build?

Our configurator checks the fit questions that matter most in a small build: processor socket, memory type, power supply wattage, clearance in the case and cooler height. Once you have picked a mini ITX case, parts that break one of those rules are flagged before you buy anything, and each part shows the prices of the shops we compare. Some things still need your own eyes. Read the case manual for the card thickness in slots, the power supply format and length, and the radiator positions, and look at a finished build in your exact case to see how the cables are routed. A check can tell you that a part fits. It cannot tell you how much patience assembly will take. The ready-made builds on our guides page are a quick starting point.