Why Didn't the U.S. Change to the Metric System?

The metric system has existed for more than 200 years and was first used in France in the 1790s. Although the metric system is widely used in the U.S., particularly in certain fields, it has never been legally deemed the nation's sole system of measurement.

Thomas Jefferson

In 1789, Thomas Jefferson, then the U.S. secretary of state, developed a system of measures quite similar to what would become the metric system. Congress, however, never adopted it into law as the nation's only system of measurement.

Current Legal Status

According to the U.S. Metric Association, the Metric Conversion Act (passed in 1975; amended in 1988) states that the metric system is the nation's preferred measurement system and that the government encourages its use.

Consumer Resistance

Despite the metric system's simplicity and widespread use around the world, U.S. consumers have resisted a wholesale conversion away from the foot, mile, pound and other non-metric measurements.

Product Labeling

In keeping with consumers' preference for familiar measurements, most consumer products created today are labeled with the non-metric measurement followed by the metric measurement in parentheses.

Fields Where Metric Measures Are Standard

In certain lines of work in the U.S., the use of metric measurements is standard. The fields of science, engineering, manufacturing and international trade depend almost entirely on the metric system.

References

• University of North Carolina, Chapel Hill: How Many? A Dictionary of Units of Measurement
• Colorado State University: U.S. Metric Association Mission and Activities