A motherboard defines CPU compatibility, RAM capacity, storage interfaces, and expansion options, which directly influence PC performance. Apart from performance, it provides features such as PCIe slots, memory channels, and I/O ports, which is why it dictates the quality and upgrade potential of your PC. When it comes to motherboards, there are standard form factors, although ATX (305 × 244 mm), Micro-ATX (244 × 244 mm), and Mini-ITX (170 × 170 mm) are the most common sizes.
What is an ATX Motherboard?
ATX motherboards are the most widely used form factor with a standard size of 305 × 244 mm. Over 60% of high-end motherboards come in this form factor and offer more PCIe lanes, memory capacity, and expansion slots than the Micro-ATX and Mini-ITX motherboards. ATX motherboards are smaller than E-ATX/Extended-ATX motherboards (305 × 330 mm) but that form factor is used mainly for flagship boards such as ASUS ROG Maximus Extreme or MSI Godlike series.
ATX motherboards standardly include 4 DIMM slots supporting up to 192 GB DDR5 or 128 GB DDR4, and there are 3 to 6 PCIe slots including x16, x4, and x1 lanes on these motherboards. The number of M.2 slots can vary, depending on the chipset, but most modern ATX motherboards come with 2–5 M.2 slots supporting PCIe Gen 4 or Gen 5.
ATX motherboards feature stronger VRM power delivery designs compared to Micro-ATX and Mini-ITX, often with 12–20+ power phases. ATX motherboards are also more efficient in thermal dissipation because of the larger surface area.
ATX motherboards fit in modern mid-tower and full-tower cases. Older cases manufactured before 2010 may not support modern ATX layouts due to 24-pin power connector placement or I/O shield differences. ATX motherboards don’t fit in small form factor cases, which is why Mini-ITX motherboards exist.
When it comes to price, ATX motherboards cost on average 20–40 USD more than Micro-ATX motherboards, although Mini-ITX motherboards can be 50–100 USD more expensive due to compact design constraints.
ATX motherboards are great for those who are willing to spend a mid-to-high budget for more expansion and better performance. ATX motherboards usually cost around 30–40 USD more than equivalent Micro-ATX models, such as ASUS TUF Gaming Z790-Plus (ATX) compared to ASUS TUF Gaming Z790M-Plus (Micro-ATX).
What is a Micro-ATX Motherboard?
Micro-ATX motherboards are smaller than ATX motherboards. A smaller motherboard size allows installation in both mid-tower and compact cases, but it offers fewer expansion options compared to ATX. The standard dimension of a micro-ATX board is 244 × 244 mm, while ATX measures 305 × 244 mm, so the difference is in both length and height.
Micro-ATX motherboards often provide two to four DIMM slots, compared to four or eight on ATX motherboards. There are usually two or three PCIe slots, such as one PCIe x16 and one or two PCIe x1 slots. Instead of six or eight SATA III ports found in most ATX motherboards, micro-ATX boards typically include four to six ports. Similarly, many modern models include one or two M.2 slots for NVMe SSDs.
Micro-ATX motherboards are positioned mainly in budget and mid-range segments, so fewer premium models exist. This limits access to advanced VRMs and high-end power delivery features, which enthusiasts and overclockers usually prefer.
The price of micro-ATX motherboards is generally lower than ATX and often lower than mini-ITX models, which makes them attractive for budget users. Micro-ATX motherboards fit well into budget-friendly mid-tower cases without requiring the full space of ATX.
Overall, a micro-ATX motherboard is most suitable when building a cost-efficient system or using a medium-sized case, while ATX is better if maximum expansion and premium features are required.
What is a Mini-ITX Motherboard?
Mini-ITX motherboards are the smallest standard consumer motherboards, measuring 170 × 170 mm, and these motherboards are designed for mini-ITX cases. Small form factor systems are commonly used in HTPC setups because compact rigs integrate better in living room environments.
A mini-ITX motherboard is smaller than an ATX and micro-ATX motherboard in both length and height. These motherboards typically include 2 DIMM slots supporting up to 64 GB of RAM, a single PCIe x16 slot, and at least one M.2 slot.
Unlike micro-ATX cases, there are several premium Mini-ITX cases available, including models such as NZXT H1 and Cooler Master NR200, which cost between $100 and $300. As expected, the performance of such motherboards is similar to their ATX counterparts, so enthusiasts frequently build compact high-end rigs with Mini-ITX motherboards.
When it comes to the compatibility of mini-ITX motherboards, these motherboards are supported by Mini-ITX cases and some mid-tower chassis with Mini-ITX mounting options. However, buying a Mini-ITX motherboard for a full-tower case provides no functional benefit.
Which Motherboard Form Factor Should You Choose?
Finalizing this article, ATX, Micro-ATX, and Mini-ITX motherboards differ mainly in size, expandability, and price-performance balance. ATX motherboards measure 305 × 244 mm and provide up to 7 PCIe slots, making them suitable for users who require higher performance, multi-GPU setups, or additional storage options.
The Micro-ATX motherboards measure 244 × 244 mm, usually include 4 PCIe slots and 4 RAM slots, and cost less than ATX boards while offering most standard features needed for gaming and office PCs. Their smaller footprint supports compact mid-tower cases.
The Mini-ITX motherboards are 170 × 170 mm with a single PCIe slot, support 2 RAM slots, and are priced higher per feature compared to Micro-ATX. They are best for small form factor builds such as HTPCs or portable gaming systems, while still supporting high-end CPUs and GPUs if cooling allows.
