Page 6 - Practical Petroleum Geology, 2nd Edition

Units of Measurement
Petroleum Extension-The University of Texas at Austin

hroughout the world, two systems of measurement dominate: the English
Tsystem and the metric system. Today, the United States is one of only
a few countries that employ the English system.
The English system uses the pound as the unit of weight, the foot as
the unit of length, and the gallon as the unit of capacity. In the English
system, for example, 1 foot equals 12 inches, 1 yard equals 36 inches, and 1
mile equals 5,280 feet or 1,760 yards.
The metric system uses the gram as the unit of weight, the metre as the
unit of length, and the litre as the unit of capacity. In the metric system, 1
metre equals 10 decimetres, 100 centimetres, or 1,000 millimetres. A kilo-
metre equals 1,000 metres. The metric system, unlike the English system,
uses a base of 10; thus, it is easy to convert from one unit to another. To
convert from one unit to another in the English system, you must memorize
or look up the values.
In the late 1970s, the Eleventh General Conference on Weights and
Measures described and adopted the Systeme International (SI) d’Unites.
Conference participants based the SI system on the metric system and de-
signed it as an international standard of measurement.
The Rotary Drilling Series gives both English and SI units. And because
the SI system employs the British spelling of many of the terms, the book
follows those spelling rules as well. The unit of length, for example, is metre,
not meter. (Note, however, that the unit of weight is gram, not gramme.)
To aid U.S. readers in making and understanding the conversion system,
we include the table on the next page.

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