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Form Factor Table

Form factor Width (inches) Length (inches) Design type
IBM PC 8.5 13 Motherboard
IBM PC XT 8.5 13 Motherboard
AT0 12 11-13 Motherboard
Baby AT 8.5 10-13 Motherboard
LPX 9 11-13 Backplane
Micro-AT 8.5 8.5 Motherboard
ATX 12 9.6 Motherboard
Mini-ATX 11.2 8.2 Motherboard
Mini-LPX 8-9 10-11 Backplane
Micro-ATX 9.6 9.6 Motherboard
NLX 8-9 10-13.6 Backplane
Flex-ATX 9 7.5 Motherboard
Mini-ITX 6.7 6.7 Motherboard
Nano-ITX 4.7 4.7 Motherboard


A backplane is a circuit board into which other circuit boards can be plugged.

The form factor usually defines a motherboard's size, shape and how it is mounted to the case, but now includes:

  • size, shape and function of the system case
  • type, placement and size of the power supply
  • system power requirements
  • location and type of external connectors
  • case airflow and cooling systems.

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