When I was a kid, we started learning the metric system in school. There was an actual plan. America was going to join the rest of the world and switch from the imperial system — the one built on the length of some king’s foot — to a logical base-ten system that scientists, engineers, and pretty much every other country on earth had already figured out. It made sense. It was going to happen.
And then it just didn’t.
I was too young at the time to understand why. Looking back at the actual history, it’s a story that tells you a lot about how this country makes decisions — or fails to.
Three countries in the world have not officially adopted the metric system as their primary standard: the United States, Myanmar, and Liberia. Every other country on Earth uses metric. Before anyone brings up England, they’re officially metric and have been since the 1960s and 70s. They’ve got cultural holdovers — road signs in miles, pints at the pub, “a stone” for body weight — but the official system is metric. Brexit had nothing to do with it. If anything, post-Brexit some British conservatives floated bringing back imperial measurements as a symbolic middle finger to the EU, which tells you something about who tends to romanticize old measurement systems and why.
So: us, Myanmar, and Liberia. Proud company.
The US has technically been legal metric since 1866 — the Metric Act of that year made it legal to use metric in commerce. The real push, the one I half-remember from school, came from the Metric Conversion Act of 1975, signed by Gerald Ford. It declared metric the “preferred” system and created the US Metric Board to manage the transition. The fatal word in that legislation was voluntary. Congress stripped enforcement out before passing it — no mandates, no deadlines, nothing binding. The legislative equivalent of telling a kid to clean their room and then leaving for the week. Predictably, not much happened. Reagan dissolved the US Metric Board in 1982, quietly, on the grounds that it wasn’t accomplishing anything. He had a point about the board. He drew the wrong conclusion about the project.
There was one follow-up. The Omnibus Trade and Competitiveness Act of 1988 re-designated metric as the preferred system for federal agencies and required federal contractors to use it. So legally, on paper, the federal government prefers metric. Go ask someone at a construction site how that’s going.
One of the arguments that killed the transition — and kept killing it every time someone tried to revive it — was the cost of replacing highway signs. The actual number is more interesting than you’d think. According to a 1995 GAO report to Congress, nobody knew. No comprehensive national estimate existed. Most states hadn’t even done preliminary work. Alabama had calculated about $70 per sign as part of an AASHTO case study, and working from a federal estimate of roughly 6 million signs on state and local roads, GAO ballparked a national total somewhere between $334 million and $420 million, and was careful to call it a soft guesstimate. So the number that killed American metrication — the scary, too-expensive-to-think-about number — was a rough extrapolation from one state’s data, never verified nationally, and reliably cited by people who didn’t want to do it anyway.
Take the high end and call it $420 million.
In 1999, NASA lost a spacecraft. The Mars Climate Orbiter had been traveling for nine months. It reached Mars, attempted orbital insertion, and burned up in the atmosphere. $327 million, destroyed. The reason: one engineering team at Lockheed Martin was sending thruster data in imperial units, and the navigation team at NASA’s Jet Propulsion Laboratory was receiving it as metric. Nobody caught it. The spacecraft approached Mars at the wrong angle and was never heard from again.
We spent $327 million on a spacecraft that could have been saved by the metric system, and we’ve spent decades refusing to spend $420 million — spread across 50 states, phased over years, with signs that need replacing on routine maintenance cycles anyway — to actually adopt it. The road sign math was never the real reason.
There is, by the way, exactly one stretch of continuous highway in the United States where road signs are in metric: Interstate 19 in Arizona, running 63 miles from Tucson down to the Mexican border. The signs went up in 1980, right at the peak of the metric push. Then the push died, the rest of the country moved on, and I-19 just stayed metric. The perfect kicker: Arizona has been trying to convert it back to miles for years and it keeps failing, because hotels and restaurants along the route advertise using the kilometer-based exit numbers and don’t want to change their marketing. We have one highway that went metric and now can’t go back, while the country went the other direction entirely. I’m not sure if that’s funny or depressing. Probably both.
So why did it really die
The construction and trades industries lobbied hard, with legitimate concerns about retooling, retraining, and standardized fittings and lumber dimensions. Small business owners didn’t want the expense of recalibration. State highway officials were alarmed by sign costs they couldn’t afford without federal help, and Congress wasn’t offering federal help. Real objections, even when the dollar amounts were inflated.
Something else was running underneath all of it. The Reagan era brought with it a particular brand of American exceptionalism — the idea that adapting to the rest of the world was inherently a concession, a sign of weakness, an elitist project dreamed up by technocrats who didn’t understand real Americans. Metric became a proxy. Not consciously, not in an orchestrated way, but in that ambient cultural way where politicians read the room, see what’s making their base angry, and quietly let the thing die rather than spend any capital defending it.
It was arguably one of the earlier examples of a move that would become very familiar: take something practical and evidence-based, reframe it as a culture-war flashpoint, and watch the merits stop mattering. “They want to change how we measure things” slides easily into “they want to change who we are.” Once it’s framed that way, you’re not really debating centimeters anymore.
We’ve seen the playbook run on bigger stages since — climate science, public health, education standards. The metric fight didn’t invent the tactic, but in hindsight it looks like an early rehearsal, proof that you could get regular people genuinely angry about abandoning something objectively more complicated in favor of something objectively simpler, if you packaged the resistance correctly.
The name itself should have been the tell. Imperial. It’s right there in the word. The system we’re so attached to was formalized by the British Empire in 1824 — the British Weights and Measures Act — explicitly to standardize measurements across the colonies. We fought a revolution to get out from under that empire and kept its rulers. The US doesn’t even use the original British imperial system exactly; it’s drifted enough that what we call “imperial” and what Britain historically called “imperial” aren’t quite the same thing anymore. We’re preserving a colonial measurement system the former colonizers themselves have mostly abandoned, which is less heritage than inherited stubbornness.
What I keep coming back to is that the metric system is easier. That’s not an opinion. It’s base ten. Everything scales by factors of ten. One unit of length, one unit of volume, one unit of mass, all relating to each other logically. Water freezes at zero and boils at 100. The whole thing was designed to make sense. Imperial is a historical accident — twelve inches to a foot, three feet to a yard, 1,760 yards to a mile, teaspoons to tablespoons to cups to pints to quarts to gallons, ounces that mean different things depending on whether you’re measuring weight or liquid. It exists because that’s what we inherited, not because anyone thought it was a good idea.
The generation that grew up metric in France or Germany or Japan doesn’t think in metric — they just think. The conversion happens automatically, the way it does for any language you grow up speaking. We decided that wasn’t worth the transition cost for our kids or their kids or their kids after that.
Canada — our neighbor, sharing the longest border in the world with us — converted their highway signs in 1977. Per the GAO’s own report, the changeover took roughly two months and cost about $13.4 million in 1995 dollars. Two months. We’ve been “thinking about it” since 1866.
I don’t know that we’re ever going to do this. The moment has probably passed in a way that would take a generational coordinated effort to reverse. Science, medicine, military, international trade — all metric. The average American doesn’t run into the collision between the systems unless they’re working in a technical field, traveling abroad, or trying to figure out why their car’s torque specs are in Newton-meters while the hardware store sells bolts by the inch.
But every once in a while I think about that Mars orbiter — $327 million tumbling through space, destroyed by a unit conversion error. And I think about the highway sign estimate that helped kill metrication, which was at best a rough guess pulled from one state’s data. We refused to spend $420 million (maybe) to do the smart thing. Then we spent $327 million (definitely) because we hadn’t done it.
Even that's Odd 
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