Measures and mistakes due to our lack of the metric system


The scene when the Spinal Tap’s manager discovers the prop is MUCH smaller than he expected.

In a scene in Rob Reiner’s mockumentary, This Is Spinal Tap, the rock group’s manager (played by Tony Hendra) goes to pick up a piece of scenery that is meant to evoke Stonehenge in connections with one of the group’s songs. He indicates that he’s quite pleased with the model with which he’s been presented with until he finds out that it is the finished piece and not a model. He expected something 18 feet high, not 18 inches high.

The designer (played by Anjelica Huston) seeks to defend herself and pulls out the napkin she’d been given to work from to show that the specifications indicated 18″ by 18″. She’d done exactly as instructed.

Closeup of napkin with specifications

A zoom in on the napkin held in the character’s hand reveals the specifications she was given was, in fact, not 18 feet but 18 inches.

Within our measurement system, the difference between (“) and (‘)* is huge. In fact, the difference is 279.4 mm or 11 inches!

“Well,” defenders of our current measures might say, “that was done for comic effect and bears no relationship to the real world.”

I beg to differ by way of an example supplied to me by a coworker.

Her husband needed a metal bar fabricated and specified on the order “3/4″ x 3/4” x 1/2′ Long.” However, instead of getting a bar that was three-quarters of an inch wide and three-quarters of an inch thick and six inches long, he instead received a small block since the (1/2’), or a half foot, direction was read instead as part of an inch rather than part of a foot.

Shows the instructions

The instructions as provided to the fabricators.

Photo of small aluminum block.

Instead of a six-inch-long bar, he ended up with a block slightly smaller than an inch in all dimensions.

As if that isn’t confusing enough, the (“) and (‘) symbols can denote both lengths and durations. Thus, 5’ 4” could mean either five feet and four inches or five minutes and four seconds if there were no context indicating which measure was intended.

So, along with the many stumbling blocks of education and medicine, and other errors related to commerce, this particular vendor had to record the original order as a loss and make and send an item that actually conformed to what the customer had originally specified.

Such errors would be greatly reduced if orders were written in “mm” for the measures rather than in the easily mistaken (“) and (‘) units.

Thus, the order could have been written: “19.05 mm x 19.05 mm x 152.4 mm.”

A lot less ambiguous.

I wasn’t able to find any information on how frequently such errors are made, but if I only had to look to the office next to mine to find an example, can they be very far away from any of us in this country?

Close up of ruler with metric and customary units.

U.S. rulers often contain a confusing mix of whole, half, quarter, eighth and sixteenth units. Metric system rulers usually just mark on the whole (10) and half (5) counts.

In conducting research for this piece, I also came across information related to “how to read a ruler/tape measure.” One source went into detail about how to distinguish between the half- and quarter-inch marks on such tools. In contrast, metric system-based rules only have differing marks to help count the “fives” and “tens.”

As I continue to look, the more examples I find of how we’re making our lives more difficult since we don’t use the metric system exclusively in this country.

Have an example of confusion/problems you’ve encountered due to our lack of metric system adoption you’d like to share? Feel free to comment on this page or send an email to me at

Stay tuned. Right now I’m researching our very early history with the metric system in this country. Luckily, prior to the last metric system push in the mid-1970s, our government put out a 200+ page document that goes into just such history. I’m now rereading it within the context of the book I’m writing.

Thanks for getting all the way down here.


* Note: Marks for feet and inches should always be indicated by straight lines, rather than by using quotation marks, which are usually curved. Did I have to look up how to make the straight lines to indicate feet and inches to write this article? Yes, yes I did.













5 thoughts on “Measures and mistakes due to our lack of the metric system

  1. “Thus, the order could have been written: “19.05 mm x 19.05 mm x 152.4 mm.””

    “A lot less ambiguous.”

    But, a lot more clumsy and nonsensical.

    This is exactly why metrication failed in the US. Americans were told nothing would change but the numbers. Simple numbers would not only be loaded with decimal dust, but would not be found on standard tape measures and rulers.

    Thus the order should have been written as 20 mm x 20 mm x 150 mm. Us the KISS principle.

  2. I know very well how to read a tape measure. I’ve been doing it all my life…. and I still get frustrated every time I have to double check the little tic marks and count the 16ths or 32nds (depending on the resolution of the tape.) I agree that the simple grouping of 5 is much better. In fact, when I was a machinist I used decimal inches. Even a scale (ruler) marked with 10ths of an inch was much easier to read than a fractional scale.

    But this is more about powers of two fractions not being a customary division for metric. Of course, decimal (powers of ten fractions) can be done with all units of measure, metric or otherwise.

  3. I was born in a metric country (India) but somehow find the usage of US units peculiar and “cute”. Most foreigners are puzzled by US units and try to avoid them as much as possible.

    Not me personally. I have taught myself to think in terms of feet, inches, miles, acres, ounces, pounds, Fahrenheit and fluid ounces. My Android GPS is set to miles and feet. I have not used kilometers in a very long time. I usually express weight in pounds and ounces along with grams and milligrams.

    But I have a hard time visualizing cubic inches, miles per gallon (miles per liter would be OK with me), cubic feet, pounds per square inch (tire pressure), British Thermal Units (everyone uses KJoules) and other dinosaur-era units. Also, it’s difficult to visualize nautical miles, US tons, gallons, pints (except when it pertains to beer and cider) and quarts (what is that?). The Brits still express their weights in terms of stones (14 lb) which is extremely annoying.

    However, I am all for diversity in weights and measures despite a few inconveniences. In India, we commonly use lakhs (or lacs) and crores to express large numbers. [1 lakh/lac = 100,000, 1 crore = 10,000,000]. It’s not going to change anytime soon.

    I am pro-metric when it comes to science education. But for everyday life, I believe one shouldn’t mind too much. Just use a calculator.

  4. Our metric system was created during the pre-revolution times, that of people of Voltaire, Blaise Pascal size among several other scientists of the “Siècle des Lumières”. They actually sent a team in the Andes to measure one 1/4 of the earth meridian. There is a vast amount of litterature about this splendid adventure. Please have a look at it. The standard iridiated platinum meter is exhibited at the Pavillion de Breteuil (at Sèvres). I have seen it.

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