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Choose an SFX PSU by matching its rated output to the complete PC build—not by applying a wattage rule based on the SFX form factor. Start with the graphics-card maker’s PSU recommendation for your CPU class, account for the rest of the components, then verify that the PSU fits the case and has the right GPU cable. A calculator is a useful starting point, not a universal answer.
How much wattage does your build need?
There is no single wattage requirement for SFX power supplies. SFX describes a PSU form factor; the necessary output depends on the particular CPU, GPU, and other parts in the system. Begin with the GPU manufacturer’s recommendation for the planned CPU class, then use a component calculator and check the result against your full parts list.
Published recommendations show why the CPU and GPU combination matters. ASUS lists 750 W for an RTX 5080 paired with an Intel Core i5 or AMD Ryzen 5 class CPU, while its table gives higher recommendations for several higher CPU classes. Corsair’s support article, updated June 9, 2025, attributes an 850 W RTX 5080 recommendation to NVIDIA. These are manufacturer-specific recommendations, not guarantees that the same wattage suits every build. ASUS’s GPU power-requirements table and Corsair’s GPU wattage guide provide the details.
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- Identify the exact CPU and GPU. Check the GPU maker’s PSU guidance for the CPU class in your build. If different manufacturer guidance does not match, treat each as guidance for its own assumptions rather than averaging the numbers.
- Account for the whole system. Include motherboard, memory, storage drives, fans, cooling, expansion cards, and peripherals. Seasonic’s calculator requests CPU, GPU, storage, cooling, peripherals, and whether the PSU is SFX or ATX/EPS. ASRock notes that its recommendations include headroom for other system components. Seasonic’s wattage calculator and ASRock’s PSU Selection Guide explain their approaches.
- Use a calculator result as a baseline. Seasonic describes its calculator output as the minimum required power for stable operation under load. The company says its calculator includes reserve for peak loads and future upgrades, while also advising that high-end GPUs, overclocking, or planned upgrades may call for additional capacity. The calculator’s result is Seasonic’s guidance for its tool, not a universal engineering standard. Read Seasonic’s calculator FAQ.
- Choose a rated output that meets the applicable recommendation. Consider whether your build includes unusually power-hungry parts, overclocking, or upgrades you actually plan to make. Avoid choosing a PSU solely because its wattage equals a calculator’s minimum if the component makers or your intended configuration call for more.
Current GPU wattage examples
The figures below are manufacturer recommendations, not universal sizing rules. CPU class and the rest of the system can change the appropriate recommendation. Verify current guidance for the exact GPU before buying.
#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.
| GPU | Published recommendation | Source and qualification |
|---|---|---|
| GeForce RTX 5090 | 1,000 W | Corsair’s support article, updated June 9, 2025, attributes this recommendation to NVIDIA. |
| GeForce RTX 5080 | 850 W | Corsair’s support article, updated June 9, 2025, attributes this recommendation to NVIDIA. ASUS varies its recommendation from 750 W to 1,000 W across listed CPU classes. |
| GeForce RTX 5070 Ti | 750 W | Seasonic guide based on GPU-maker data; the current page does not state a publication year. |
| GeForce RTX 5070 | 650 W | Seasonic guide based on GPU-maker data; the current page does not state a publication year. |
| Radeon RX 9070 XT | 750 W | Seasonic guide. ASUS lists 750 W for lower CPU classes and 850 W for higher CPU classes. |
Sources: Corsair, Seasonic, and ASUS.
Check SFX case fit separately from wattage
A PSU can have enough rated output and still be unsuitable if the case does not support its form factor or it does not physically fit. Confirm the case’s supported PSU type and the unit’s dimensions. Also consider cable routing and available clearance around the GPU; compact cases can make these practical constraints important.
Seasonic’s calculator distinguishes SFX from ATX/EPS, but the calculator cannot confirm that a particular unit fits your case. Check the case and PSU manufacturer specifications for the exact models. Do not assume that a wattage tier or the SFX label alone establishes physical compatibility.
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
Verify GPU connectors and PSU cables
Check the exact PSU’s included connectors against the GPU’s requirements. Current GPU guidance may call for a 12VHPWR or 12V-2×6 connection. Seasonic describes these connector systems as capable of supplying up to 600 W to a graphics card; that is the connector’s stated capacity, not the total wattage requirement of the PC. Seasonic’s ATX 3.1 explanation covers the connector context.
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Do not assume modular PSU cables are interchangeable between models, even if a connector appears to fit. Use only cables confirmed for the exact PSU model and revision. Corsair’s SF850 product page, for example, specifies an included PCIe 5.1 12V-2×6 GPU cable. Check the SF850 product specifications for that particular model.
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.
Compare PSUs beyond their wattage rating
When two models appear to meet the build’s wattage requirement, compare the attributes that determine whether each is appropriate and trustworthy. Manufacturer claims and certifications do not replace independent testing, and the sources cited here do not establish a performance or noise ranking among SFX models.
- Continuous rated output and how it compares with the build’s component guidance.
- Case-supported form factor, exact dimensions, and cable clearance.
- GPU connector provision and cable compatibility with the exact PSU.
- ATX and PCIe standard compatibility where relevant to the planned GPU.
- Efficiency certification, warranty, and price and availability.
- Independent electrical and noise test results for the specific model, if available.
The Corsair SF850 is one example of an SFX PSU, not a universal recommendation: Corsair specifies 850 W output, ATX 3.1 compliance, a PCIe 5.1 12V-2×6 cable, and a seven-year warranty. Those specifications do not show that 850 W suits every high-end GPU or every SFX case. Confirm the product details with Corsair and check compatibility against your own parts.
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Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
