Cubic Inch (in³)
The cubic inch, symbol in³, is a US customary and imperial unit representing the volume of a cube with each side one inch in length. Its use dates back centuries in English measurement systems. Today, it is particularly significant in the automotive industry, where it historically defined engine displacement before metric liters became common. One cubic inch equals 16.387 milliliters, making it a small but practical unit for precision engineering, manufacturing, and certain niche applications.
Imperial Gallon (imp gal)
The imperial gallon, shown as imp gal, is a British unit equal to 4.54609 liters. It came from English wine and drink measures in the 1800s and became official in 1824. The imperial gallon was used throughout the British Empire and is still used in the UK and some other countries for fuel and beverages. The liter is now used almost everywhere, but the imperial gallon still exists because of custom and local use.