Micro-ATX (µATX) is a motherboard form factor introduced by Intel in 1997. It measures 244 millimetres square, making it significantly smaller than full-size ATX boards (305 × 244 mm) but larger than Mini-ITX (170 × 170 mm).
The smaller size means fewer expansion slots and sometimes fewer memory slots, but Micro-ATX boards retain most of the features found on standard ATX motherboards. They typically include four RAM slots, multiple USB headers, and space for a dedicated graphics card. This makes them a practical choice for builds that don't need maximum expandability.
Micro-ATX motherboards fit into compact PC cases designed for the form factor, helping you build a smaller system without sacrificing too much functionality. For example, a business workstation or a modest gaming PC can use a Micro-ATX board in a case roughly 20 litres in volume, rather than the 40+ litres needed for a full ATX build.
When buying, check that your case is rated for Micro-ATX: cases often support multiple sizes, but not all do. Also verify the motherboard has the ports and slots you need, since you'll have fewer expansion options than with ATX. Micro-ATX is a sensible middle ground if you want a compact build but need more connectivity than Mini-ITX offers.