Form factor refers to the size, shape and physical specifications of hardware or hardware components. Standardized computer form factors are necessary to ensure the physical compatibility between the different components in your computer systems. Having the correct form factor is vital for connection compatibility. 

Importance of form factors

The most obvious example of a computer form factor is the difference between components made for a desktop versus a laptop computer. Although the same parts are present in each, they’re shaped and sized differently. For example, keyboards for desktop computers are different than keyboards for laptop computers.  

The form factor of any hardware component is dependent on, and influenced by, the form factor of the components that it interacts with. This will dictate the limits of the overall size and shape of the component, as well as specifying the physical and electrical connections. Most component manufacturers have standardization rules so that component compatibility can be easily determined.

The standardization of component form factors ensures that compatible components can physically fit into the intended space, while incompatible components are prevented from doing so. For example, mini-USB ports have a form factor that prevents micro-USB connectors from being inserted into them. The electrical specifications of these two form factors are different, so they could cause damage to other components if the wrong one was inserted.  

USB-C is becoming a growing standard worldwide, able to support everything from cell phones to external hard drives in delivering data, video and power. 

A variety of cable connectors with different form factors

Computer memory form factor

Computer memory (Random Access Memory or RAM) has different form factors to prevent incompatible components from being inserted. Each generation of computer memory is made so that it cannot be inserted into a slot on a motherboard that was made for a different generation of memory. Because the electric and electronic specifications change for each generation of memory, inserting incompatible memory will, at best, not work, and at worst, cause electrical damage to the motherboard or processor. If you want to upgrade or add memory to your computer, use the Crucial System Scanner or Crucial Upgrade Selector to make sure your RAM is compatible.  

In addition to the different generations, there are different sizes and shapes of memory for different kinds of hardware. Servers, desktop computers, laptop computers, notebook computers and mobile devices all use different memory form factors. These form factors have different sizes and a different number and configuration of connection pins. Read more about the different types of RAM

A diagram which indicates how the physical shape of memory has changed per generation

Solid State Drive (SSD) form factors

The same concept exists for SSDs. There are different sizes and connections for different generations of technology and different hardware applications. 

SATA SSDs

SATA SSDs use the SATA connectors on a motherboard, just like older spinning disk hard drives. These SSDs measure 2.75 x 3.95 inches and are commonly 7mm (0.27 inches) or 15mm (0.6) inches thick. SATA SSDs are inexpensive, light and easy to install, but they have limited performance compared to NVMe drives. 

M.2 NVMe SSDs

M.2 form factor NVMe SSDs are much smaller than SATA drives and use a different interface called Non-Volatile Memory Express (NVMe). Instead of using cables, these drives mount directly to the motherboard. NVMe drives are typically 22mm wide (0.86 inches) and either 80mm (3.15 inches) or 30mm (1.18 inches) long, although other dimensions are available.  

The measurements form part of the name of the form factor, so a 2280 NVMe drive is 22mm wide and 80mm long, while a 2230 NVMe drive is 22mm wide and 30mm long. Longer drives can hold more chips, and therefore can have a greater capacity.  Read more about the difference between SATA and NVMe SSDs, and learn more about what an NVMe SSD is here. 

Crucial solid state drives.

Motherboard form factors

Motherboard form factors also vary in physical size and in the number and kind of electric and electronic connections.   

The shape and size of the motherboard will determine the CPU, memory modules, storage drives, expansion cards and peripherals that can be attached to the computer. The most common types of desktop motherboard form factors are ATX, microATX, Mini-ITX and NUC.  

ATX (Advanced Technology eXtended) form factor motherboards were introduced in 1995 by Intel and today are one of the most widely used standards for desktop computers. ATX motherboards offer ample space for multiple expansion slots, such as PCIe slots for graphics cards, sound cards and other peripherals. They typically support up to four RAM modules and have multiple connectors for storage drives. Because of its design and large size, ATX allows for excellent airflow and space for cable management, making it ideal for high-performance systems that require significant cooling.  

Size: 305 x 244 mm (12 x 9.6 inches) 
Use case: Full-sized desktops, gaming PCs and workstations  

microATX motherboards are a smaller version of the ATX form factor. They retain much of the functionality of the larger ATX boards, but typically have fewer expansion slots and connectors. They still offer a good balance between size and expandability, making them suitable for users who need a moderately powerful system but want to save space. For many users, a graphics card is the only expansion card they’ll add, so the microATX format is sufficient. microATX motherboards are commonly found in budget and mid-range builds. microATX boards are often also compatible with cases designed for full-size ATX motherboards.  

Size: 244 x 244 mm (9.6 x 9.6 inches) 
Use case: Compact desktops, budget gaming PCs and home office computers  

Mini ITX (Mini Information Technology eXtended) is a compact form factor designed for maximum space efficiency. They typically only include a single PCIe slot, two RAM slots and limited connectors for storage devices. Despite their small size, many Mini ITX motherboards support powerful CPUs and GPUs, making them popular for small form factor builds where portability and minimal desk space are key considerations. They are ideal for users who need a compact yet capable system for gaming, media streaming or light productivity.  

Size: 170 x 170 mm (6.7 x 6.7 inches) 
Use case: Small Form Factor (SFF) PCs, home theater PCs (HTPCs), and portable gaming rigs  

NUC (Next Unit of Computing) form factor motherboards, developed by Intel, are an ultra-compact motherboard standard designed for minimalist computing needs. NUC motherboards are typically integrated into small, box-like enclosures with limited expandability. They are ideal for basic computing tasks, media playback and embedded applications. NUC systems often come with soldered CPUs, onboard memory and integrated graphics, making them non-upgradable, but highly energy efficient. Their small footprint allows them to be mounted behind monitors or placed in tight spaces. Although small and inexpensive, many will support multiple monitors, DDR5 RAM and fast SSDs, which can make them extremely capable machines for users who don’t need access to the most powerful graphics options.  

Size: Typically around 102 x 102 mm (4 x 4 inches) 
Use case: Ultra-compact PCs, digital signage, kiosks, low-power desktops and home theatre PCs   

If you want to upgrade your computer or build your own, it's important to know the form factors of the components you choose. There is a wide range of memory and storage products, so it’s easy to find the perfect option for your system. Use the Crucial System Scanner or Crucial Upgrade Selector to get guaranteed compatibility for your upgrades. 

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