Motherboard Form Factors: ATX, Micro ATX, Mini ITX

What is a motherboard form factor

A motherboard form factor is a standard that defines the board's dimensions, mounting hole locations, and the position of key connectors. These standards ensure that a motherboard fits into a case designed for that form factor and that the power supply and other components align correctly. For a gaming PC, the form factor influences how many components you can install and the overall size of the system.

Three form factors dominate the desktop gaming market: ATX, Micro ATX (often written mATX), and Mini ITX. Each serves a different balance of expansion capability and physical footprint. To see how these sizes translate into complete systems, browse the best prebuilt gaming PCs or the best gaming motherboards.

ATX: the full-size standard

ATX (Advanced Technology eXtended) is the largest common form factor, measuring 305 mm by 244 mm. It provides the most room for expansion: typically seven PCIe slots, four RAM slots, and multiple M.2 and SATA connectors. This makes ATX the preferred choice for builds that include multiple graphics cards, high-end CPU coolers, or many storage drives.

Most full-tower and mid-tower cases support ATX motherboards. The extra space also allows for better airflow around components and easier cable management. For a gaming PC that prioritizes maximum performance and future upgrade options, ATX is the standard. If you are looking for a prebuilt with this level of expansion, check the best 4K gaming PCs which often use ATX boards.

• Dimensions: 305 mm x 244 mm
• PCIe slots: up to 7
• RAM slots: typically 4
• Best for: high-end gaming, multi-GPU setups, extensive storage

Micro ATX: the balanced option

Micro ATX shrinks the board to 244 mm x 244 mm, reducing the number of expansion slots to four (or sometimes three) while keeping the same mounting hole pattern as ATX. This means a Micro ATX board fits into most ATX cases as well as smaller Micro ATX cases. It usually includes two to four RAM slots and a reasonable number of SATA and M.2 ports.

For many gamers, Micro ATX offers a good compromise: enough slots for a single graphics card, a Wi-Fi card, and a capture card, without the extra bulk of a full ATX board. It also enables smaller case builds that are easier to transport or fit on a desk. Many mid-range prebuilt systems, such as those in the best 1440p gaming PCs, use Micro ATX boards to balance cost and expandability.

• Dimensions: 244 mm x 244 mm
• PCIe slots: up to 4
• RAM slots: typically 2 to 4
• Best for: mid-range gaming, compact builds, single-GPU setups

Mini ITX: the smallest form factor

Mini ITX is the most compact standard, measuring 170 mm x 170 mm. It has only one PCIe slot (usually a PCIe x16 for the graphics card) and two RAM slots. The small size limits the number of storage drives and expansion cards you can install, but it allows for very small cases that can sit on a desk or fit into a backpack.

Mini ITX builds require careful component selection because the tight space can restrict CPU cooler height, GPU length, and power supply size. However, modern Mini ITX cases and components have made it possible to build a powerful gaming PC in a very small footprint. This form factor is ideal for gamers who value portability or a minimalist setup. For prebuilt options in this size, explore the best esports gaming PCs, which often feature compact designs.

• Dimensions: 170 mm x 170 mm
• PCIe slots: 1
• RAM slots: 2
• Best for: small form factor (SFF) gaming, travel, space-saving

Case compatibility and expansion

The motherboard form factor dictates which cases it can be installed in. ATX cases accept ATX, Micro ATX, and Mini ITX boards. Micro ATX cases accept Micro ATX and Mini ITX boards. Mini ITX cases accept only Mini ITX boards. Always check the case specifications for supported form factors before choosing a motherboard.

Expansion is directly tied to form factor. ATX boards offer the most PCIe slots for adding sound cards, capture cards, or additional storage controllers. Micro ATX boards provide enough for most gamers, while Mini ITX boards limit you to the single slot used by the graphics card. If you plan to use multiple graphics cards or many add-in cards, ATX is the only practical choice. For guidance on matching a motherboard to your needs, see the best gaming motherboard guide.

What to pick for your play

The right form factor depends on your gaming habits, space constraints, and upgrade plans. The table below matches common scenarios to the recommended form factor and guides you to the best prebuilt gaming PCs for each size.

What to pick for your play

Questions

Can I fit a Micro ATX motherboard in an ATX case?

Yes. ATX cases have mounting holes for both ATX and Micro ATX boards. The board will be smaller, leaving extra space inside the case, which can improve airflow but may look less full.

Can I fit an ATX motherboard in a Micro ATX case?

No. Micro ATX cases are too short to accommodate the full length of an ATX board. Always match the motherboard form factor to the case's supported sizes.

Does motherboard form factor affect gaming performance?

No. The form factor does not directly affect frame rates or game performance. It only determines the physical size and expansion capabilities. Performance depends on the CPU, GPU, RAM, and storage.

Which form factor is best for a single graphics card build?

Micro ATX is often the best balance for a single GPU build. It provides enough slots for the graphics card and a few extras, fits in a mid-tower case, and leaves room for good airflow.

Are Mini ITX motherboards more expensive than ATX?

Mini ITX motherboards can be more expensive for equivalent features because the compact design requires more engineering. However, prices vary by chipset and brand.

Can I use a full-size power supply with a Mini ITX motherboard?

It depends on the case. Some Mini ITX cases accept standard ATX power supplies, while others require smaller SFX or SFX-L units. Always check the case specifications.

Do all motherboards of the same form factor have the same mounting holes?

Yes. The mounting hole positions are standardized within each form factor. ATX, Micro ATX, and Mini ITX each have a fixed pattern, ensuring compatibility with cases that support that size.

Which form factor is best for a quiet gaming PC?

ATX or Micro ATX in a case with good airflow and sound dampening. Larger cases allow for larger, slower-spinning fans that produce less noise. Mini ITX builds can be more challenging to keep quiet due to tighter airflow.