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PC Chassis and Motherboard Size Guide

Motherboard Form Factor Size Guide Schematic

1. Measure your Internal Chassis Clearance

Before purchasing a new motherboard, measure the “tray” area of your PC chassis. While most modern cases are categorized as Mid-Tower or Full-Tower, internal clearances vary. Check the distance from the rear I/O shield cutout to the front drive cages. A standard ATX board requires 305mm of vertical height, but ATX Ultra or XL-ATX variants can exceed 340mm.

2. Identify Standoff Mounting Points

Motherboards are secured by brass spacers called standoffs. Look for etched letters: ‘A’ for ATX, ‘M’ for Micro-ATX, and ‘I’ for ITX. Proper alignment ensures your board is grounded and prevents electrical shorts.


The Rise of ATX Ultra and XL-ATX

For the extreme enthusiast, standard ATX is often not enough. ATX Ultra (or XL-ATX) is designed for motherboards with more than four PCIe lanes. These boards typically measure around 345 x 262 mm.

Using an ATX Ultra board provides expansion for NVMe RAID cards and multi-GPU setups but creates a “clearance crisis” in standard Mid-Towers. Ensure your chassis has 8 or 9 expansion slots; a standard Mid-Tower only has 7, meaning an Ultra board will physically hit the PSU shroud.


The Versatility of the Mid-Tower Chassis

The Mid-Tower is the “goldilocks” of PC hardware. It fits high-end cooling without dominating your desk. Most Mid-Towers house Standard ATX motherboards, but modern “Panoramic” designs now prioritize width for side-mounted radiators.

Always ensure your Mid-Tower has at least 160mm of CPU cooler clearance. Narrower cases may prevent the side panel from closing if using high-end air coolers like the Noctua NH-D15.


Airflow Optimization in Mid-Tower Builds

In a Mid-Tower, the goal is Positive Pressure: more intake than exhaust. This forces air out of every gap, preventing dust buildup.

We recommend a “Front-to-Back” path. Intake fans at the front pull cool air; exhaust fans at the rear expel heat from the CPU and VRMs. If using a Micro-ATX board in a Mid-Tower, use the extra bottom space for additional intake fans to keep your GPU cool.


ITX vs mITX: Clarifying the Naming

A frequent point of confusion is ITX vs mITX. These terms are used interchangeably for the Mini-ITX form factor (170mm x 170mm). While “mITX” is technically more accurate, “ITX” is the common shorthand at ShopiShop. These boards feature a single PCIe slot, perfect for Small Form Factor (SFF) builds.


Comprehensive Compatibility Table

Form Factor Dimensions (mm) Compatible Chassis
XL-ATX / Ultra 345 x 262 Full Tower
E-ATX 305 x 330 Full Tower
ATX 305 x 244 Mid-Tower
Micro-ATX 244 x 244 Mini / Mid-Tower
Mini-ITX / mITX 170 x 170 SFF / Mid-Tower

Expert Recommended Hardware

Best Mid-Tower (ATX)

Best Compact (mATX)

Best SFF (Mini-ITX)


Hardware Compatibility Help

WhatsApp Advice: +27 87 092 7908

Chassis & Mid-Towers

Why choose a Mid-Tower over a Full-Tower?
Mid-Towers offer the best balance of space and footprint. They fit most office furniture while supporting standard ATX boards and large GPUs.

Will an ATX Ultra board fit my Mid-Tower?
No. ATX Ultra boards need 8-9 expansion slots; Mid-Towers only have 7. It will hit the PSU shroud.

Motherboard Tech

Is there a difference between ITX and mITX?
No, they are identical. mITX is the technical name for Mini-ITX, and ITX is the shorthand.

Can I put a Micro-ATX board in a Mid-Tower?
Absolutely. Most Mid-Towers have pre-drilled holes for both ATX and Micro-ATX.

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