Cubic inch
Encyclopedia
The cubic inch is a unit of measurement for volume
Volume
Volume is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance or shape occupies or contains....

in the Imperial units and United States customary units
United States customary units
United States customary units are a system of measurements commonly used in the United States. Many U.S. units are virtually identical to their imperial counterparts, but the U.S. customary system developed from English units used in the British Empire before the system of imperial units was...

systems. It is the volume of a cube with each of its 3 sides being one inch
Inch
An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...

long.

The cubic inch and the cubic foot
Cubic foot
The cubic foot is an Imperial and US customary unit of volume, used in the United States and the United Kingdom. It is defined as the volume of a cube with sides of one foot in length.-Conversions:- Symbols :...

are still used as units of volume in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, although the common SI
International System of Units
The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...

units of volume, the liter
Litér

, milliliter, and cubic meter, are continually replacing them, especially in manufacturing
Manufacturing
Manufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale...

and high technology.

One cubic foot is equal to exactly 1728 cubic inches because 123 = 1728.

## Notation conventions

The following symbols have been used to denote the cubic inch:
• cubic in
• cu inch, cu in
• inch^3, in^3
• inch³, in³
• c.i., CI
• cui
• c.i.d., cid, CID —for cubic inch displacement
Engine displacement
Engine displacement is the volume swept by all the pistons inside the cylinders of an internal combustion engine in a single movement from top dead centre to bottom dead centre . It is commonly specified in cubic centimeters , litres , or cubic inches...

in internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

s

## Equivalence with other units of volume

1 cubic inch (assuming an international inch
Inch
An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...

) is equal to:
• 0.000578703703703 cubic feet (1 cu ft
Cubic foot
The cubic foot is an Imperial and US customary unit of volume, used in the United States and the United Kingdom. It is defined as the volume of a cube with sides of one foot in length.-Conversions:- Symbols :...

equals 1728 cu in)
• roughly 1 tablespoon
Tablespoon
A tablespoon is a type of large spoon usually used for serving. A tablespoonful, the capacity of one tablespoon, is commonly used as a measure of volume in cooking...

(1.0 US gallon = 256 US tablespoons = 231 cubic inches)
• about 0.554112552 American/English fluid ounce
Fluid ounce
A fluid ounce is a unit of volume equal to about 28.4 mL in the imperial system or about 29.6 mL in the US system. The fluid ounce is distinct from the ounce, which measures mass...

s
Cup (unit)
The cup is a customary unit of measurement for volume, used in cooking to measure liquids and bulk foods such as granulated sugar...

s
Bushel
A bushel is an imperial and U.S. customary unit of dry volume, equivalent in each of these systems to 4 pecks or 8 gallons. It is used for volumes of dry commodities , most often in agriculture...

s
• about 0.004329 American liquid gallon
Gallon
The gallon is a measure of volume. Historically it has had many different definitions, but there are three definitions in current use: the imperial gallon which is used in the United Kingdom and semi-officially within Canada, the United States liquid gallon and the lesser used United States dry...

s (1.0 gallon equals 231 cu in exactly [3 in × 7 in × 11 in])
Barrel
A barrel or cask is a hollow cylindrical container, traditionally made of vertical wooden staves and bound by wooden or metal hoops. Traditionally, the barrel was a standard size of measure referring to a set capacity or weight of a given commodity. A small barrel is called a keg.For example, a...

s of crude oil (1.0 barrel equals 42 gallons, by definition, or 9702 cu in)
• exactly 0.016387064 liter
Litér

(1.0 liter is about 61 cu in [exactly 61.0237440947323 cu in])
• exactly 16.387064 milliliters or cubic centimeters (which in turn is approximately 0.061 cu in)
• exactly 0.000016387064 cubic meters (1.0 m³ is about 61,023.74 cu in)

### Electrical box volume

The cubic inch was established decades ago 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

The cubic inch was formerly used by the automotive industry
Automotive industry
The automotive industry designs, develops, manufactures, markets, and sells motor vehicles, and is one of the world's most important economic sectors by revenue....

and aircraft industry
Aircraft industry
The aircraft industry is the industry supporting aviation by building aircraft and manufacturing aircraft parts for their maintenance. This includes aircraft and parts used for civil aviation and military aviation. Most production is done pursuant to type certificates and Defense Standards issued...

in North America (through the early 1980s) to express the nominal engine displacement
Engine displacement
Engine displacement is the volume swept by all the pistons inside the cylinders of an internal combustion engine in a single movement from top dead centre to bottom dead centre . It is commonly specified in cubic centimeters , litres , or cubic inches...

for the engines of new automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

s, truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...

s, aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft 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.Although...

, etc. Hence the cubic inch is still used for this purpose in the context of classic car collecting and so forth. The auto industry now uses liters for this purpose (and the use of reciprocating engines for commercial and military airplanes and helicopters has disappeared, having been replaced by turbojet, turboprop
Turboprop
A turboprop engine is a type of turbine engine which drives an aircraft propeller using a reduction gear.The gas turbine is designed specifically for this application, with almost all of its output being used to drive the propeller...

, and gas turbine
Gas turbine
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....

engines).

For more information and a list of cubic-inch-to-liter displacement conversions, see engine displacement.

• Orders of magnitude (volume)
Orders of magnitude (volume)
The pages linked in the right-hand column contain lists of volumes that are of the same order of magnitude . Rows in the table represent increasing powers of a thousand. -Notes:...

• Conversion of units
Conversion of units
Conversion of units is the conversion between different units of measurement for the same quantity, typically through multiplicative conversion factors.- Process :...

• Square inch
Square inch
A square inch is a unit of area, equal to the area of a square with sides of one inch. The following symbols are used to denote square inches:*square in*sq inches, sq inch, sq in*inches/-2, inch/-2, in/-2...

• Cubic foot
Cubic foot
The cubic foot is an Imperial and US customary unit of volume, used in the United States and the United Kingdom. It is defined as the volume of a cube with sides of one foot in length.-Conversions:- Symbols :...