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 US dry gallon is a unit of volume in the US customary unit system with the symbol dry gal.
The dry gallon is equal to 268.8025 in³ or 4.404 L.
The US dry gallon is not used anywhere any more - the unit below is the dry pint and the unit above is the bushel.