What is the difference between SFX and ATX power supplies?

The primary difference is size. ATX is the standard desktop form factor (150mm x 86mm x 140mm+), whereas SFX is designed for small form factor cases (125mm x 63.5mm x 100mm). SFX units use smaller fans (usually 80-92mm) and shorter cables.

Can I install an SFX PSU in an ATX case?

Yes, but you will need an SFX-to-ATX adapter bracket. Many premium SFX power supplies include this bracket in the box. You may also need cable extensions since SFX power cables are significantly shorter than standard ATX cables.

SFX vs ATX PSU: Form Factors & Mounting Guide

Dimensions Comparison

The physical volume comparison between these two standards is substantial:

ATX (Advanced Technology eXtended): 150 mm width × 86 mm height × 140 mm (to 200 mm) depth.
SFX (Small Form Factor): 125 mm width × 63.5 height × 100 mm depth.

SFX power supplies are roughly half the volume of a standard ATX unit, freeing up critical space for airflow and routing in Mini-ITX cases (such as the Lian Li A4-H2O or Fractal Ridge).

Cable Length & Mounting Templates

Because SFX units are destined for tight spaces, their modular cables are typically 300mm to 400mm long, compared to 600mm+ on standard ATX power supplies.

⚠ Cabling Tip: If you install an SFX unit in a Mid-Tower ATX case, the 24-pin motherboard cable or 8-pin EPS CPU cable may not reach their respective sockets. You will need sleeved extension cables in this scenario.

Cooling and Fan Profile

ATX power supplies can accommodate 120mm to 140mm fans, which move large volumes of air at low RPMs, keeping operation silent. SFX units are limited to 80mm or 92mm fans, which must spin faster (generating a higher-pitched sound profile) to maintain safe thermal limits.

Check your build clearances