In the never-ending drama that is Brexit, Prime Minister Boris Johnson has floated a proposal to allow the U.K.’s vegetable and fruit vendors to use non-metric units like ounces and pounds. David Frost, the government minister overseeing the exit from the European Union, described the move as an effort to “capitalize on new Brexit freedoms.”

It’s also evidence that clumsy old systems of weights and measures have always had remarkable staying power despite the metric system’s self-evident advantages. Which means that Johnson’s move may be more than posturing. It may usher in a revival of old-fashioned units of measurement.

There’s no disputing that the metric system is more rational and coherent. Every unit relates to the others in a predictable fashion, all driven by powers of 10. In many ways, it resembles Esperanto, a language designed to be consistent and easy to learn. Esperanto never gained a significant following. Neither did the metric system when it was first introduced.

In the 18th century, France was infamous for having thousands of different weights and measures with ancient, feudal origins. In some cases, the names of units differed from village to village. In others, the name was the same, but the units were different in size or scale. The rest of continental Europe was also saddled with a dizzying diversity of weights and measures.

The outbreak of the French Revolution in 1789 brought a decisive break with the past. Changes  included abolishing the monarchy in September 1792, an event commemorated by the creation of a new calendar that marked the date as the beginning of “year one.”

The revolutionaries also turned their attention to weights and measures, and this was no minor reform. One typical proclamation expressed rage that the “friends of equality” might continue to “suffer the most inconvenient ragbag of measures, which preserves vestiges of feudal serfdom.” The revolutionaries adopted a new method of measurement devised by the French philosophes: the metric system. They distributed meters, kilograms and liters throughout the land. Problem solved!

Actually, no. As the historian Witold Kula has chronicled, the new system sowed endless confusion. What looked rational and obvious from the standpoint of elite thinkers proved problematic in practice. Asking peasants and provincial officials to throw out units of measurement that had served them for centuries provoked intense resistance.

This was understandable. Weights and measures are like languages: difficult to learn as an outsider, but intuitive for native speakers and woven into the fabric of everyday life.

A French peasant could easily calculate in units that might require doubling or halving something — or working in 12ths or even 20ths — as demanded by the existing units. But the new idea that everything could be reduced to powers of 10 was alien. What had formerly been “half a quarter” was now rendered as 0.125. Even the units — cent, kilo, deci — seemed strange.

And people hated it. Most ignored the new weights and measures. When forced to use them, local administrators converted them back into the older units. Napoleon himself sanctioned the continued use of traditional measures. In 1812, one official captured the state of affairs in France when he observed that the metric units were not “well adapted to the daily dealings of the common people, who have much difficulty in understanding and applying decimal divisions.”

The metric system eventually secured a foothold in France, but this had little to do with its inherent virtues. Rather, it was a testament to the tenacity of administrators in Paris, who relentlessly pushed the system for 50 years, constantly on the lookout for backsliding. Despite these efforts, the dawn of the 20th century found many of the older units still in use, though they had begun, at long last, to die out.

Other countries that adopted the metric system went through comparable tribulations. The process usually took a century or more, as ordinary people wedded to older units — and no less important, the prices of goods or commodities denominated in those units — refused to get with the metric program.

Resistance sometimes turned violent. In 1874 and 1875, rioters in Brazil smashed and destroyed kilogram weights that had been introduced by representatives of the central government. Their movement, known as “Quebra-Quio” — “smash the kilos” — arose at a sensitive moment in the nation’s development, as the government tried to impose a new system of taxation and new forms of land tenure along with the new systems of measurement. For the peasants who rose up in revolt, this was all of a piece: an attack on their way of life.

In many metric countries, the new units never fully supplanted the older ones. The historian Hector Vera has shown how Mexico, which made the metric system optional in 1857 and compulsory in 1896, still continues to use non-metric units in a number of contexts. Seamstresses measure women’s clothing in centimeters, but tailors measure men’s clothing in inches. Many other examples confirm that the metric system is less an exclusive system of measurement than what Vera aptly describes as the “predominant” system.

Britain, like France, once used a confusing array of local weights and measures inherited from medieval times. But in 1824, while the metric system was still a work in progress, Britons brought order to their measures by defining three key units: the yard, troy pound and gallon. All other units were defined by these three.

This workmanlike reform may have lacked the panache of the metric system, and it took another half-century to take root. As the French had found, declarations and laws mean little if people continue to speak in the language of older units. Nonetheless, by the early 20th century, Britons had achieved a level of consistency and uniformity that rivaled the French. But the language of measurement was different.

Britain was hardly alone. The world’s largest economy, the U.S., remained wedded to older units derived from British precedent, and repeatedly rejected attempts to make the metric system compulsory. As in Britain, certain professions and industries — medicine, electrical engineering, pharmaceuticals — adopted the metric system, but most did not.

In the closing decades of the 20th century, both countries took small steps toward a metric future. As a condition of its membership in the EU, the U.K. grudgingly began to phase out the imperial units. But the metric system has shallow roots there. The older units lived on in the minds of ordinary people. If given the opportunity to use them again, they will almost certainly do so.

When it comes to weights and measures, never underestimate the pull of the past.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

Stephen Mihm, a professor of history at the University of Georgia, is a contributor to Bloomberg Opinion.

More stories like this are available on

©2021 Bloomberg L.P.