What's wrong with the Imperial (British) system of measurement?
(Why Imperial unit questions in calculus classes can be confusing.)
• Conversions have strange factors (1 mile = 5280 feet).
• Basic units can mean several things (there are 4 quarts, 3 tons, 2 miles, 3 barrels, etc.).
Americans contribute to this anarchy by using their own gallons.
• Obscure names and conversions for larger or smaller units (12 lines = 1 in).
• The pound is a unit of weight not mass; the unit of mass is obscure (a slug).
• Liquid volume and distance units are not related (whereas in the metric system 1 ml = 1 cm^3 ~= 1 gm water).
• Electric units do not exist since Volt, Amp, Ohm, etc. are metric.
• Clarity of thought is impeded by the disorganization of the system. For a simple minded example consider this: It is difficult to convert the price of crude oil per barrel into a price per gallon and so it is difficult to compare price changes in crude with price changes at the pump.
• Metric units are more fundamental in the sense that many of the imperial units are defined in terms of metric units (1 in = 2.54 cm exactly)
• Unfortunately imperial units will never disappear. For example, in Alberta land has been surveyed in square miles and related units, so the distance between country roads is in multiples of miles typically.
Further details:
``` 4 quarts:
Imperial quart     1.136 l
Imperial wet quart     ? l
US dry quart       1.102 l
US wet quart        .95  l
3 barrels:
Imperial           1636  l
US                  119  l
US petro.           158  l
2 miles:
land:     5280 ft = 1 mile
nautical: 6075 ft = 1 mile     (fathom = 2 yards)
3 tons:
long              1016 kg
short              907 kg
register           2.8 m^3
3 pounds:
troy (for gold)
avoirdupoid (for drugs)
ordinary
Obscure conversions:
640 acres per mile^2 (why 640?)  versus  hectare = (1/10 km)^2
Obscure units:
weight: beside pounds there are stones (= 14 pound), grains, dram and ounce.
liquid volume: gill (= 1/4 pints), peck (= 2 gal), bushel (= 4 peck),
and in Imperial useage: quarter (= 8 bushels),
barrel (= 45 bushels)
```

Last update: 2001 December 23