ATX vs Micro-ATX vs mini-ITX: which size?

The three sizes

ATX is 305 × 244 mm and is the standard full-size board. Micro-ATX is 244 × 244 mm, a shorter board with fewer slots. Mini-ITX is 170 × 170 mm, the smallest of the three. EATX is bigger than ATX, at about 305 × 330 mm, and is found on workstation and enthusiast boards.

Expansion slots and memory

Bigger boards have more room for expansion. ATX boards usually have up to seven slots for cards and four memory slots, Micro-ATX usually has up to four slots and two or four memory slots, and mini-ITX has a single graphics card slot and two memory slots. For a gaming PC with one graphics card, all three have what you need.

Price and features

ATX boards tend to offer the most M.2 drive slots, USB ports and power delivery for overclocking. Micro-ATX boards cost less and keep most of the useful features. Mini-ITX boards pack those features into a tiny board and often cost more for their size.

Which one should you choose?

Choose ATX if you want the most ports, storage and upgrade room. Choose Micro-ATX if you want a slightly smaller, cheaper build that still has plenty of room. Choose mini-ITX only if you want a very small PC and are happy to work in tight spaces.

A case rated for ATX also fits Micro-ATX and mini-ITX boards, so buying an ATX-rated case keeps your options open.