The cubic inch is a unit of volume derived from the imperial unit system and uses the symbol in³.
1 cubic inch is defined as equal to the volume of a cube with edges measuring 1 in. It is equivalent in volume to 16.387 ml, 1/231 US gallons and 1/1728 ft³.
Common uses for cubic inches include quantifying the size of electrical boxes and in the automotive industry for measuring engine displacement. The 5th generation Ford Mustang ran on a Boss 302 which was a 302 in³ engine (5.0L).
The register ton is a unit of volume in the shipping world and uses the symbol GRT.
1 register ton is equal to 100 ft³ or 2.832 m³.
The register ton is used in shipping to measure the amount of cargo on a vessel. The phrase is often mistaken for a unit of mass or weight because of the term 'ton' but should not be confused.