> I have been researching US non-metric definitions. > > Handbook 130 says a US gallon is 231 cubic inches. > http://ts.nist.gov/ts/htdocs/230/235/h130-03/07_IV_PackLabReg.pdf > > Federal standard 376 says it is 3.785412 liters > http://ts.nist.gov/ts/htdocs/200/202/fs376-b.pdf > > There is a small difference between the two values. Is the US gallon > precisely defined in terms of cubic inches or liters?
AFAIK, the US gallon is precisely defined as 5/6 imperial gallon, and the imperial gallon is exactly 10 pounds of water (presumably at 4C).
