The US measures, not surprisingly, derive from those in use in England before the
revolution. Of course, this was before the French revolution (1789), when most European
countries used proper systems of measurement, instead of the so-called 'metric'
system. The act of 1824 which had such an impact in England was of course after the
revolution, so the Americans didn't benefit from the general tidying-up that it
introduced. The main similarities and differences are as follows:
- Lengths. These are the same in both systems, i.e inch, foot, yard, mile.
- Weights. Up to and including the pound, the two systems are the same. The
Americans never use the stone as a weight, which is in universal use in England
(especially to weigh people). The hundredweight (cwt) in England is always 112
pounds, or 8 stone. In the US, the hundredweight is 100 lb, unless noted as otherwise.
It is proper to call a 100 lb hundredweight a short hundredweight, and a 112 lb one a
long hundredweight. As there are always 20 cwt to the ton, in the US it is
normal to use a 2000 lb ton (a short ton), and in England a 2240 lb ton (a
- Liquid measures. In England, since 1824, liquid and dry measures have
been the same. The gallon in use in the US is for liquid measure only. It is the
old 'Queen Anne' gallon, of 1707, and is of 231 cubic inches. The Imperial gallon
is bigger at 277.4194 cubic inches. As there are 8 pints to the gallon, the pint is
different in the two systems - 28.875 cu. in. for the US, 34.677425 cu. in. for
the Imperial. In the US there are 16 fl. oz. to the pint, the Imperial has 20, so
the two fluid ounces are very close.
- Dry measures. US dry measures are not the same as US liquid measures. The US (dry) bushel is that of William III of 1696, and is of 2150.42 cu. in. The Imperial bushel is 8 Imperial gallons, or 2219.3552 cu. in. In the Imperial system, dry and liquid measures use the same units.