SFX (Small Form Factor) PSUs measure 125 × 63.5 × 100 mm — roughly half the volume of a standard ATX PSU — and output identical power via standard ATX connectors. Required for Mini-ITX SFF cases where an ATX PSU physically cannot fit. SFX-L (125 × 63.5 × 130 mm) adds 30 mm of depth to accommodate a 120 mm fan for better thermals at higher wattage. Leading SFX and SFX-L units: Corsair SF750 (SFX-L, 750W), Seasonic Focus SGX-650 (SFX), Lian Li SP750 (SFX), Fractal Design Ion SFX 650G.
| S F X Dimensions | 125 × 63.5 × 100 mm |
| S F X- L Dimensions | 125 × 63.5 × 130 mm |
| Fan Size ( S F X- L) | 120 mm |
| Max Wattage (common) | 500–750 W (SFX), up to 1000 W (SFX-L) |
| Use Case | Mini-ITX and SFF builds |