This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.Find sources: "Cubic inch" – news · newspapers · books · scholar · JSTOR (February 2022) (Learn how and when to remove this template message)
Cubic inch
An engine with a swept piston displacement of 502 cubic inches
General information
Unit systemNonstandard
Unit ofvolume
Symbolin3 or cu in
1 in3 in ...... is equal to ...
   SI derived units   16.387 mL
   US customary   1231 US Gallon
   nonstandard   11728 ft3

The cubic inch (symbol in3) is a unit of volume in the Imperial units and United States customary units systems. It is the volume of a cube with each of its three dimensions (length, width, and depth) being one inch long which is equivalent to 1/231 of a US gallon.[1]

The cubic inch and the cubic foot are used as units of volume in the United States, although the common SI units of volume, the liter, milliliter, and cubic meter, are also used, especially in manufacturing and high technology. One cubic inch is approximately 16.387 mL.

One cubic foot is equal to exactly 1,728 cubic inches (28.32 L) because 123 = 1,728.[citation needed]

One U.S. gallon is equal to exactly 231 cubic inches (3.79 L).[citation needed]

Notation conventions

Equivalence with other units of volume

1 cubic inch (assuming an international inch) is equal to:

Uses of the cubic inch

Electrical box volume

The cubic inch was established decades ago in the National Electrical Code 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

Main article: Engine displacement

North America

The cubic inch was formerly used by the automotive industry and aircraft industry in North America (through the early 1980s) to express the nominal engine displacement for the engines of new automobiles, trucks, aircraft, 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 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 has a "Challenger 392" (a conversion from its 6.4 liter V8 engine).

United Kingdom

In the UK, engine displacement is now denoted in litres. However, cubic inches were sometimes used in the past to denote model numbers. An example is the AEC Reliance bus which was available with five different engines:

See also


  1. ^ a b "260.1-2004 - IEEE Standard Letter Symbols for Units of Measurement (SI Customary Inch-Pound Units, and Certain Other Units)". 2004-09-24. Retrieved 2022-02-08.