Are All PSU the Same Size

Are All PSU the Same Size?

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When building or upgrading a computer, the power supply unit (PSU) is a crucial component. It provides the electrical power needed to run all the other parts of your PC. But have you ever wondered are all PSU the same size? In this comprehensive guide, we’ll explore the world of PSU sizes, their variations, and what you need to know to ensure compatibility with your system.

Understanding PSU Sizes

Before we dive into the specifics of PSU sizes, let’s establish a basic understanding of what PSU sizes entail. PSU size refers to the physical dimensions of the power supply unit. The size of a PSU can vary significantly between different models and manufacturers. The size of your PSU is crucial because it determines whether it will fit inside your computer case and whether it can provide enough power for your components.

Different PSU Sizes


The most common PSU size you’ll encounter is the ATX (Advanced Technology Extended) PSU. These PSUs typically measure around 5.9 x 3.4 x 5.5 inches (150 x 86 x 140 mm). ATX PSUs are widely used and fit into most standard ATX cases.

2. Micro ATX PSU

For smaller PC cases, there are Micro ATX PSUs. These units are more compact, measuring approximately 5.1 x 2.5 x 4.9 inches (130 x 63.5 x 125 mm). They are designed to fit into Micro ATX and Mini-ITX cases.


If you’re building a compact PC, you might need an SFX (Small Form Factor) PSU. These PSUs are even smaller than Micro ATX units, measuring roughly 4.9 x 2.5 x 2.5 inches (125 x 63.5 x 63.5 mm). They are ideal for Mini-ITX cases and compact builds.


TFX (Thin Form Factor) PSUs are often used in slim and low-profile cases. They measure approximately 6.1 x 3.3 x 2.8 inches (155 x 83.5 x 70 mm). TFX PSUs are designed to fit into cases with limited space.

5. Custom Sizes

In addition to the standard sizes mentioned above, some manufacturers produce custom-sized PSUs for specific cases. These PSUs can vary in dimensions, so checking compatibility before purchasing is essential.

Compatibility Factors

Now, let’s address the primary question: Are all PSU the same size? The answer is no; PSUs come in various sizes, and their compatibility with your system depends on several factors:

1. Case Compatibility: The first and most crucial consideration is whether your computer case can accommodate the size of the PSU you want to use. Most cases are designed to fit standard ATX PSUs, but smaller cases may require SFX or SFX-L PSUs.

2. Mounting Orientation: Some PSUs are designed to be mounted in different orientations, such as top-mounted or bottom-mounted. Ensure your case supports the orientation of your chosen PSU.

3. Wattage Requirements: The size of your PSU can also affect its wattage output. Smaller PSUs may provide less power than their larger counterparts. Make sure the PSU you choose can meet the power demands of your components.

PSU Form Factors and Cases

In addition to ATX, SFX, and SFX-L, there are other less common PSU form factors, such as TFX, Flex ATX, and more. These form factors cater to specific niche cases and may not be widely compatible with standard consumer cases. When considering a non-standard form factor, ensure that your case and motherboard can accommodate it.

PSU Size and Wattage

It’s essential to understand that PSU size is not the sole determinant of its wattage or power output. While larger PSUs may offer higher wattage options, smaller PSUs can still provide ample power for most systems. When selecting a PSU, pay close attention to its wattage rating to ensure it meets your needs.

Choosing the Right PSU Size

To choose the right PSU size for your build, follow these steps:

1. Check Your Case: Determine your case’s maximum PSU size. Refer to your case’s manual or specifications.

2. Consider Future Upgrades: If you plan to upgrade your components in the future, choose a PSU with some headroom in terms of wattage to accommodate potential additions.

3. Evaluate Power Requirements: Calculate the total power requirements of your components, including the CPU, GPU, drives, and other peripherals. Choose a PSU with sufficient wattage to cover your needs.

4. Check Compatibility: Ensure that the PSU form factor and connectors are compatible with your motherboard and other components.

PSU Size Myths Debunked

Thereare a couple of myths surrounding PSU size that need to be debunked:

1. Bigger PSU is Always Better: While a larger PSU can provide more power, it’s not always necessary. Using a vastly oversized PSU can be inefficient and may lead to higher energy bills.

2. Smaller PSUs are Inadequate: Smaller PSUs, such as SFX or SFX-L, are perfectly capable of powering even high-end gaming systems. Don’t underestimate their capabilities based solely on size.


In conclusion, not all PSU sizes are the same. The size of your power supply unit is an important consideration when building or upgrading your computer. It determines whether it will fit in your case, whether it can provide enough power to your components, and whether it’s compatible with your motherboard.

When choosing a PSU, carefully assess your case’s compatibility, power requirements, and any future upgrade plans. By selecting the right PSU size, you can ensure a stable and efficient power supply for your computer.


1. Can I use an ATX PSU in a Mini-ITX case?

In most cases, an ATX PSU will not fit in a Mini-ITX case due to size constraints. You’ll need to use an SFX or SFX-L PSU designed for compact cases.

2. Are SFX-L PSUs more powerful than SFX PSUs?

SFX-L PSUs are not inherently more powerful than SFX PSUs. Both can offer various wattage options. The key difference is the physical size, with SFX-L PSUs being slightly longer.

3. Should I always choose the highest wattage PSU available?

No, you should choose a PSU with wattage that matches your system’s power requirements. Using a significantly higher wattage PSU than necessary can be inefficient and more expensive.

4. Are there any advantages to using a smaller PSU in a larger case?

Using a smaller PSU in a larger case can create more space for airflow and cable management. However, make sure the smaller PSU provides sufficient power for your components.

5. Can I use a non-standard PSU form factor in a standard case?

It’s generally not recommended to use non-standard PSU form factors in standard cases, as they may not fit or align correctly with the case’s PSU mounting points. Always check compatibility before purchasing a PSU.

Last Updated on 24 February 2024 by Ansa Imran


Ansa Imran, a writer, excels in creating insightful content about technology and gaming. Her articles, known for their clarity and depth, help demystify complex tech topics for a broad audience. Ansa’s work showcases her passion for the latest tech trends and her ability to engage readers with informative, well-researched pieces.

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