Form factor is a hardware

design A design is a plan or specification for the construction of an object or system or for the implementation of an activity or process or the result of that plan or specification in the form of a prototype, product, or process. The verb ''to design'' ...

aspect that defines and prescribes the size, shape, and other physical specifications of components, particularly in

electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

. A form factor may represent a broad class of similarly sized components, or it may prescribe a specific standard. It may also define an entire system, as in a computer form factor.

Evolution and standardization

As electronic hardware has become smaller following

Moore's law Moore's law is the observation that the number of transistors in a dense integrated circuit (IC) doubles about every two years. Moore's law is an observation and projection of a historical trend. Rather than a law of physics, it is an empi ...

and related patterns, ever-smaller form factors have become feasible. Specific technological advances, such as

PCI Express PCI Express (Peripheral Component Interconnect Express), officially abbreviated as PCIe or PCI-e, is a high-speed serial computer expansion bus standard, designed to replace the older PCI, PCI-X and AGP bus standards. It is the common m ...

, have had a significant design impact, though form factors have historically been slower to evolve than individual components.

Standardization Standardization or standardisation is the process of implementing and developing technical standards based on the consensus of different parties that include firms, users, interest groups, standards organizations and governments. Standardization ...

of form factors is vital for compatibility of hardware from different manufacturers.

Trade-offs

Smaller form factors may offer more efficient use of limited space, greater flexibility in the placement of components within a larger assembly, reduced use of material, and greater ease of transportation and use. However, smaller form factors typically incur greater costs in the

manufacturing Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a ...

, and maintenance phases of the engineering lifecycle, and do not allow the same expansion options as larger form factors. In particular, the design of smaller form-factor computers and network equipment must entail careful consideration of cooling.

End-user In product development, an end user (sometimes end-user) is a person who ultimately uses or is intended to ultimately use a product. The end user stands in contrast to users who support or maintain the product, such as sysops, system administrato ...

maintenance and repair of small form-factor electronic devices such as mobile phones is often not possible, and may be discouraged by

warranty In contract law, a warranty is a promise which is not a condition of the contract or an innominate term: (1) it is a term "not going to the root of the contract",Hogg M. (2011). ''Promises and Contract Law: Comparative Perspectives''p. 48 Cambri ...

voiding Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis ...

clauses; such devices require professional servicing—or simply replacement—when they fail.

Examples

Computer form factors comprise a number of specific industry standards for

motherboard A motherboard (also called mainboard, main circuit board, mb, mboard, backplane board, base board, system board, logic board (only in Apple computers) or mobo) is the main printed circuit board (PCB) in general-purpose computers and other expand ...

s, specifying dimensions,

power supplies A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a r ...

, placement of mounting holes and ports, and other parameters. Other types of form factors for computers include: * Small form factor (SFF), a more loosely defined set of standards which may refer to both motherboards and

computer case A computer case, also known as a computer chassis, is the enclosure that contains most of the hardware of a personal computer. The components housed inside the case (such as the CPU, motherboard, memory, mass storage devices, power supply unit ...

s. SFF devices include mini-towers and

home theater PC A home theater PC (HTPC) or media center computer is a convergent device that combines some or all the capabilities of a personal computer with a software application that focuses on video, photo, audio playback, and sometimes video recording ...

s. *

Pizza box form factor In computing, a pizza box is a style of case design for desktop computers or network switches. Pizza box cases tend to be wide and flat, normally in height, resembling pizza delivery boxes and thus the name. This is in contrast to a tower sy ...

, a wide, flat case form factor used for computers and network switches; often sized for installation in a

19-inch rack A 19-inch rack is a standardized frame or enclosure for mounting multiple electronic equipment modules. Each module has a front panel that is wide. The 19 inch dimension includes the edges or "ears" that protrude from each side of the equ ...

. * All-in-one PC * "Lunchbox"

portable computer A portable computer is a computer designed to be easily moved from one place to another and included a display and keyboard together, with a single plug, much like later desktop computers called '' all-in-ones'' (AIO), that integrate the ...

Components

* Hard disk drive form factors, the physical dimensions of a computer hard drive * Hard disk enclosure form factor, the physical dimensions of a computer hard drive enclosure * Motherboard form factor, the physical dimensions of a computer motherboard

Mobile form factors

* Laptop or notebook, a form of portable computer with a "

clamshell design The flip phone or clamshell is a form factor of a mobile phone or other device which is in two or more sections that fold via a hinge. If the hinge is on a long edge the device is more likely to be called clamshell than flip phone (e.g., ...

" form factor. * Subnotebook, ultra-mobile PC,

netbook Netbook was a commonly used term that identified a product class of small and inexpensive laptops which were sold from 2007 to around 2013. These machines were designed primarily as cost-effective tools for consumers to access the Inte ...

, and

tablet computer A tablet computer, commonly shortened to tablet, is a mobile device, typically with a mobile operating system and touchscreen display processing circuitry, and a rechargeable battery in a single, thin and flat package. Tablets, being comput ...

, various form factors for devices which are smaller and often cheaper than a typical notebook. * Mobile phone form factor, comprising the size, shape, layout, and style of mobile phones. Broad categories of form factors include bars,

flip phones The flip phone or clamshell is a Form factor (mobile phones), form factor of a mobile phone or other device which is in two or more sections that fold via a hinge. If the hinge is on a long edge the device is more likely to be called clamshe ...

, and sliders, with many subtypes and variations of each. *

Stick PC A stick PC or PC on a stick is a single-board computer in a small elongated casing resembling a stick, that can usually be plugged directly (without an HDMI cable) into an HDMI video port. A stick PC is a device which has independent CPUs or proce ...

, a

single-board computer A single-board computer (SBC) is a complete computer built on a single circuit board, with microprocessor(s), memory, input/output (I/O) and other features required of a functional computer. Single-board computers are commonly made as demonstrat ...

in a small elongated casing resembling a stick

Notes

References

{{reflist Design Electronic design Industrial design Packaging Broad-concept articles