The following content is going to talk about the ATX motherboard dimensions of the standard type as well as the variants. If you are interested in more details about the ATX motherboard or similar knowledge, you can just visit MiniTool disk partition software website.

About ATX (Advanced Technology eXtended)

According to Wikipedia, ATX is a configuration specification of the motherboard and power supply invented by Intel in 1995. It was the first major change in the motherboard, power supply and desktop computer enclosure design for many years. ATX improves the standardization and interchangeability of computer components. It defines the dimensions, the I/O panel, the mounting points, and the power & connector interfaces within a computer host case, a motherboard as well as a power supply.

ATX Motherboard Dimensions

Just as mentioned in the above, ATX is the most common (popular) motherboard design. As for other standards for smaller boards, like microATX, mini-ITX, nano-ITX and FlexATX, they usually only keep the basic rear layout and reduce the number of the slots as well as decrease the size of the board.

ATX Motherboard Hole Dimensions

Dimensions of ATX Motherboard Variants

Just as described in the above, some smaller boards that derived from the normal ATX set different standards for the board size and smaller number of expansion slots. Yet, they make use of the same mountings, basic back panel arrangement as well as the same power supply.

The standard ATX motherboard offers 7 slots at 0.8 inches (20 mm) spacing, while the microATX reduces 3 slots of 2.4 inches (61mm). Here, the width refers to the distance along the external connector edge, while the depth refers to distance from front to rear.

Note: There once was a Mini ATX with a design of 5.9 × 5.9 in (15 × 15 cm). It was removed from the ATX specifications due to microATX was adopted. Also, the removing of MiniATX specification is to avoid contradiction to the modern Mini-ITX standard, which is of 6.7 × 6.7 in (17 × 17 cm) dimension.

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Many manufacturers have added 1, 2 or 3 additional expansion slots (with the standard 0.8-inch spacing) to the standard 12-inch ATX width. Also, there were some strange form factors in 1999 including full-size AT, Baby-AT and the semi-proprietary LPX for low-profile host cases.

Below is a picture comparing the different variants of ATX motherboard sizes. Each larger size includes all previous smaller color areas.

The following are the ATX-related motherboard dimensions including proprietary motherboards and customized motherboards for notebooks and portable computers.


Width × Depth

Maximum Size

Invented Year Manufacturer

12 × 9.6 in

(305 × 244 mm)

1995 Intel

9.9 × 9.9 in

(244 × 244 mm)

1997 Intel

9 × 7.5 in

(229 × 191 mm)

1997 Intel

Extended ATX (E-ATX)


12 × 13 in

(305 × 330 mm)

? Supermicro / Asus

Extended ATX


12 × 10.1 in

(305 × 257 mm)

12 × 10.4 in

(305 × 264 mm)

12 × 10.5 in

(305 × 267 mm)

12 × 10.7 in

(305 × 272 mm)

? ?
Enhanced Extended ATX (EE-ATX)

13.68 × 13 in

(347 × 330 mm)

? Supermicro
Ultra ATX

14.4 × 9.6 in

(366 × 244 mm)

2008 Foxconn

13.5 × 10.3 in

(343 × 262 mm)

2009 EVGA

13.58 × 10.31 in

(345 × 262 mm)

2010 Gigabyte

13.6 × 10.4 in

(345 × 264 mm)

2010 MSI
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