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What do ATX, SFX and SFX-L mean?
These labels describe the PSU’s physical form factor: its dimensions and mounting arrangement. They do not, by themselves, tell you its wattage, efficiency, connectors, noise level or quality. Those depend on the specific power-supply model.
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Corsair’s form-factor guide publishes the following dimensions. Its ATX lengths are examples because ATX PSU length varies by model.
| Form factor | Published dimensions | Typical fit | Key clearance check |
|---|---|---|---|
| ATX | 150 mm wide × 86 mm high; 140, 160 and 180 mm length examples | Cases with an ATX PSU bay | Check the exact PSU depth and room around drive cages, radiators and cables. |
| SFX | 125 × 63.5 × 100 mm | Compact cases with tighter PSU space | Confirm SFX support in the case; an ATX case may require a mounting bracket. |
| SFX-L | 125 × 63.5 × 130 mm | Compact cases that allow extra PSU length | Confirm the case explicitly supports the additional depth. |
Dimensions are from Corsair’s form-factor guide. SFX-L shares SFX’s width and height but is 30 mm longer, so a case that fits SFX may not necessarily fit SFX-L.
#1 Best Overall
- Fully Modular PSU: Reliable and efficient low-noise power supply with fully modular cabling, so you only have to connect the cables your system build needs.
- ATX 3.1 Certified: Compliant with the ATX 3.1 power standard, supporting the PCIe Gen 5.0 platform and resisting transient power spikes.
- Low-Noise Fan: Equipped with a premium 92mm FDB (Fluid Dynamic Bearing) fan, the PSU ensures efficient and quiet thermal performance.
- Native 12V-2x6 Connector: SP Series V2 Gold features a two-tone 12V-2x6 power cable with visual cues for safe connections, enhancing clarity and reliability for high-performance 50/40 series graphics cards.
- Upgraded Standby Power & Reliable Power Backed by 10-Year Hardware Protection: The SP Series V2 Gold features an upgraded 5VSB (standby) rail, increasing its current capacity from 2.5A to 3A, better supporting today's power-hungry peripherals.
Will an SFX power supply fit in an ATX case?
Often, yes, if the case has enough clearance and you use a compatible SFX-to-ATX adapter bracket. The smaller unit’s mounting holes do not line up with a standard ATX PSU opening without the bracket, as Corsair’s installation guidance explains.
The bracket solves the mounting mismatch; it does not make the cables longer or establish that the PSU can supply enough power for your system. Check cable reach to the motherboard, CPU power socket, graphics card and drives, then confirm the PSU’s wattage and connectors suit your components. Use only modular cables approved for the exact PSU model: modular PSU cables are not universally interchangeable.
Rank #2
- Compact Power Solution: APEVIA SFX-AP500W 500W Power Supply designed for Mini ITX Solution, Micro ATX, and SFX form factor systems
- Comprehensive Connector Options: Includes 1 x 20+4pin Main Power, 1 x 8pin 12V(P4+4), 1 x 6/8pin PCIe, 3 x SATA, and 2 x 4pin Molex connectors for versatile compatibility
- Space-Saving Dimensions: Measures 125mm x 100mm x 63.5mm (4.9 inches x 3.94 inches x 2.5 inches) - L x W x H, designed for small form factor builds
- Proper Installation Required: The power supply will not power on simply by connecting the power cord to both the power supply and wall outlet. Ensure that all the power supply cables are properly connected to the PC for it to power on
- Flexible CPU Power Connection: The 8pin CPU connector can be split apart to become a 4+4 by pushing one end of the 4pin down and the other end of the 4pin up for motherboards that require a 4pin power
Brackets are not universal. Match the adapter to both the PSU and the case. Corsair, for example, lists an SF Series SFX-to-ATX Adapter Bracket 2.0 for compatible SF/SF-L units; check its compatibility information rather than assuming it fits another PSU.
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Can an ATX PSU fit in a mini-ITX case?
Only if that particular case supports ATX PSUs and has room for the unit’s actual length. “Mini-ITX” describes the motherboard form factor, not a guaranteed PSU size. Compact cases differ: some provide an ATX PSU bay, while others require SFX or allow SFX-L only within a specified depth.
Rank #3
- Fully Modular PSU: Reliable and efficient low-noise power supply with fully modular cabling, so you only have to connect the cables your system build needs.
- ATX 3.1 Certified: Compliant with the ATX 3.1 power standard, supporting the PCIe Gen 5.0 platform and resisting transient power spikes.
- Low-Noise Fan: Equipped with a premium 92mm FDB (Fluid Dynamic Bearing) fan, the PSU ensures efficient and quiet thermal performance.
- Native 12V-2x6 Connector: SP Series V2 Gold features a two-tone 12V-2x6 power cable with visual cues for safe connections, enhancing clarity and reliability for high-performance 50/40 series graphics cards.
- Upgraded Standby Power & Reliable Power Backed by 10-Year Hardware Protection: The SP Series V2 Gold features an upgraded 5VSB (standby) rail, increasing its current capacity from 2.5A to 3A, better supporting today's power-hungry peripherals.
ATX PSU length varies, so the ATX label alone is not enough to establish fit. Check the case manual for supported PSU formats and maximum depth, then compare that limit with the selected PSU’s dimensions and the clearance remaining after other components are installed.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to choose the right form factor
- Check the case documentation. Find the PSU compatibility section in the manual or manufacturer’s page. Note supported formats and maximum PSU depth.
- Match the case’s stated format. If it requires SFX, choose SFX unless the manual explicitly allows SFX-L and the extra length fits. If it accepts ATX, ATX is the direct fit, subject to the exact unit’s depth.
- Account for nearby components. Check whether drive cages, radiators or other parts occupy the PSU area, and leave enough room for cable connections and routing.
- If adapting SFX to ATX, verify the bracket and cable reach. Confirm the bracket works with both the case and PSU, and that the cables reach all required components.
- Compare the specific PSU models on electrical and operational needs. Check system wattage requirements, GPU connectors, efficiency, warranty, acoustics and cable configuration. Form factor alone does not establish a performance advantage.
What form factor does not tell you
A smaller PSU is not automatically lower quality, quieter or less capable, and a larger one is not automatically better. Form factor is a fit specification. Once the case fit is confirmed, assess the individual PSU’s electrical capacity, connectors and other model-specific characteristics for your build.
Intel’s official design-guide page identifies separate ATX12V and SFX12V guidelines; it provides standards context, not a guarantee that a given case and retail PSU are physically compatible. The page also notes that a newer guide version is available, so its surfaced 2023 revision should not be treated as the latest specification: Intel Desktop Platform Form Factors Power Supply Design Guide.
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