The cubic inch (symbol in³) is a unit of volume in the

Imperial units The imperial system of units, imperial system or imperial units (also known as British Imperial or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed th ...

and

United States customary units United States customary units form a system of Units of measurement, measurement units commonly used in the United States and Territories of the United States, U.S. territories since being standardized and adopted in 1832. The United States cust ...

systems. It is the volume of a

cube In geometry, a cube is a three-dimensional solid object bounded by six square faces, facets or sides, with three meeting at each vertex. Viewed from a corner it is a hexagon and its net is usually depicted as a cross. The cube is the on ...

with each of its three dimensions (length, width, and height) being one

inch Measuring tape with inches The inch (symbol: in or ″) is a unit of length in the British imperial and the United States customary systems of measurement. It is equal to yard or of a foot. Derived from the Roman uncia ("twelft ...

long which is equivalent to 1/231 of a US gallon. The cubic inch and the cubic foot are used as units of volume in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

, although the common SI units of volume, the

liter The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3 ...

, milliliter, and cubic meter, are also used, especially in

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

high technology High technology (high tech), also known as advanced technology (advanced tech) or exotechnology, is technology that is at the cutting edge: the highest form of technology available. It can be defined as either the most complex or the newest tec ...

. One cubic inch is approximately . One cubic foot is equal to exactly because 12³ = 1,728. One US gallon is equal to exactly .

Notation conventions

* The following abbreviations have been used to denote the cubic inch: cubic in, cu inch, cu in, cui, cu. in. * The

IEEE The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operati ...

standard symbol is: in³ * In

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal co ...

s, the following abbreviations are used to denote cubic inch displacement: c.i.d., cid, CID, c.i., ci

Equivalence with other units of volume

1 cubic inch (assuming an international inch) is equal to: * (1 cu ft equals 1,728 cu in) * Roughly 1

tablespoon A tablespoon (tbsp. , Tbsp. , Tb. , or T.) is a large spoon. In many English-speaking regions, the term now refers to a large spoon used for serving; however, in some regions, it is the largest type of spoon used for eating. By extension, the ter ...

(1.0 U.S. gallon = 256 U.S. tablespoons = 231 cubic inches) * About * About * About 0.06926407 American/English cups * About * About * About * About (1.0 gallon equals 231 cu in exactly in × 7 in × 11 in * About of crude oil (1.0 barrel equals 42 gallons, by definition, or 9,702 cu in) * Exactly (1.0 liter is about ) * Exactly or cubic centimeters (which in turn is approximately ) * Exactly ( is about )

Uses of the cubic inch

Electrical box volume

The cubic inch was established decades ago in the

National Electrical Code The National Electrical Code (NEC), or NFPA 70, is a regionally adoptable standard for the safe installation of electrical wiring and equipment in the United States. It is part of the National Fire Code series published by the National Fire Pro ...

as the conventional unit in North America for measuring the volume of electrical boxes. Because of the extensive export of electrical equipment to other countries, some usage of the non-SI unit can be found outside North America.

Engine displacement

North America

The cubic inch was formerly used by the

automotive industry The automotive industry comprises a wide range of companies and organizations involved in the design, development, manufacturing, marketing, and selling of motor vehicles. It is one of the world's largest industries by revenue (from 16 % su ...

and aircraft industry in North America (through the early 1980s) to express the nominal

engine displacement Engine displacement is the measure of the cylinder volume swept by all of the pistons of a piston engine, excluding the combustion chambers. It is commonly used as an expression of an engine's size, and by extension as a loose indicator of t ...

for the engines of new

automobile A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarded ...

truck A truck or lorry is a motor vehicle designed to transport cargo, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame constructi ...

aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. ...

, etc. The cubic inch is still used for this purpose in classic car collecting. The auto industry now uses liters for this purpose, while reciprocating engines used in commercial aircraft often have model numbers based on the cubic inch displacement. The fifth generation

Ford Mustang The Ford Mustang is a series of American automobiles manufactured by Ford. In continuous production since 1964, the Mustang is currently the longest-produced Ford car nameplate. Currently in its sixth generation, it is the fifth-best selli ...

has a Boss 302 version that reflects this heritage - with a five-liter (302 cubic inch) engine similar to the original Boss. Chevrolet has also revived this usage on its 427 Corvette.

Dodge Dodge is an American brand of automobiles and a division of Stellantis, based in Auburn Hills, Michigan. Dodge vehicles have historically included performance cars, and for much of its existence Dodge was Chrysler's mid-priced brand above P ...

has a "Challenger 392" (a conversion from its 6.4 liter V8 engine).

References

{{United States Customary Units Customary units of measurement in the United States Imperial units Units of volume ja:インチ#立方インチ