The Metric Kitchen
Cooking in metric
Most nutritional information is given in grams or mg for serving sizes given in grams. The use of metric measures for this purpose without customary equivalents is ubiquitous, even in the U.S.
The Bureau International des Poids et Mesures discourages the use of the unit Calorie. There are some very good reasons for this, including the problem that there are many different definitions of the Calorie. The officially recommended unit is kilojoules, where 1 Calorie is about 4.186 kJ. If used, Calorie must either always be capitalized or, better yet, it should be written kilocalorie or kcal.
The following converter (below) will convert back and forth between kilocalories and kilojoules. Just enter a number in either field, then click outside the text box.
It's worth noting that a joule is the amount of energy used by a 1 W lightbulb in 1 second.
A brief history of the metric system from a U.S. perspective
Article I Section 8 of the U.S. constitution, written in 1787, states that "The Congress shall have Power to... fix the Standard of Weights and Measures." In 1790, Thomas Jefferson proposed replacing the traditional system of weights and measures used in the U.S. with a new decimal-based system. At the same time that Jefferson was backing a decimal-based system in the U.S., the French were actively developing a decimal system based on a meter defined as 1/10,000,000 of the distance from the equator to the north pole. While this new metric system was officially adopted in France in 1795, the drive to implement a decimal-based system in America fizzled. Over the next century, the metric system was gradually accepted for use across most of Europe.
The Metric Act of 1866 made the metric system legal for use in the United States, and made it illegal to refuse to trade or deal in metric quantities. In 1875, 18 nations, including the United States, signed the Convention of the Metre. In 1893, standards for all customary American units like the yard and the pound were officially abandoned in favor of redefining these unit in terms of the international metric standards.
In 1964, the National Bureau of Standards (now called NIST) made the metric system its standard "except when the use of these units would obviously impair communication or reduce the usefulness of a report." By the early 1970s, nearly every country on the planet except the U.S. had officially converted to the metric system, and resulting economic pressures motivated Congress to pass the Metric Conversion Act of 1975 to coordinate and plan the voluntary conversion to the metric system. This act formally designated "the metric system of measurement as the preferred system of weights and measures for United States trade and commerce." The Omnibus Trade and Competitiveness Act of 1988 strengthened the Metric Conversion Act.
Today, the U.S. is the only country in the world that is predominantly non-metric. Even the United Kingdom, which still uses some traditional measures for specific purposes (like speed limits in MPH and beer measured in pints) is predominantly metric. In the U.S., usage of the metric system is gradually increasing, and given the combination of international pressures and the inherent advantages of the metric system, this trend is certain to continue.
Weight and mass
Technically, pounds and ounces measure weight, while grams and kilograms are used to measure mass. Weight refers to how hard something pushes down from the pull of gravity. Mass refers to how much matter, independent of gravity. Thus, an 80 kg astronaut in the space station weighs 0 pounds, but his mass is still 80 kg, just like on earth. Since most of us will never be astronauts, I have called mass "weight" in these pages to try to keep things simple.
Metric system links