Imperial vs. Metric Units

Continuing a discussion from here that keeps coming up in this international forum: Why does the USA still rely on imperial units of measure? I guess the answer is “Freedom!”

Just in case no one thinks we aren’t aware or have no sense of humor, this from last week’s Saturday Night Live:

(I’m hoping YouTube doesn’t have some geofencing or something preventing people outside the US from viewing the video – let me know.)


Luckily it works here. I laughed so that the fresh stitches on my tummy almost came off.
There was an error: Inches and Centimeters do line up at places as the definition of an inch is 25.4 millimeters.

But seriously, I wonder if someone has lately done any real research about the frequency of measuring errors under the metric and imperial systems. We all have heard about the fatal ones that happened with mixups.


This is why I’ve long advocated that the US moves to using the King’s Foot measuring system. We could start with the King of Spain, Felipe VI, or any other Royal to give the system magisterial credence. I estimate from pictures that His foot is about a foot. From this new strong foundation we could transition and spearhead this new systematic way of measuring around the world. Not unlike what has been done with the metric system.

Works in the UK. Thanks for posting.

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In the Netherlands, it was introduced around 1816, but only to be official some 120 years later (1937).
Maybe it takes time. We are free to use different, but it makes not much sense to do so.

Even between villages and cities there were differences between voeten (feet) and duim (inch).
The city hall of Leiden had the Rijnlandse roede engraved in the front, divided by twelve to get the rijnlandse voet:

(Partly seen below the 1 feet handle)

Now, this feet measures 0,3139465 meter, thus when the brownist Pelgrim fathers fled from Leiden to New Amsterdam in the Mayflower, there must have been some conditions on that ship that shrunk their tools:)


This particular mixup sticks in my mind:

When I was in college, my Shigley handbook defined millimeters as 25.4001 per inch. Wikipedia gives this account: “In 1946, the Commonwealth Science Congress recommended a yard of exactly 0.9144 metres for adoption throughout the British Commonwealth. This was adopted by Canada in 1951; the United States on 1 July 1959; Australia in 1961, effective 1 January 1964; and the United Kingdom in 1963, effective on 1 January 1964. The new standards gave an inch of exactly 25.4 mm, 1.7 millionths of an inch longer than the old imperial inch and 2 millionths of an inch shorter than the old US inch.”


Now that makes my brain hurt.

Even just within the imperial system, working with feet AND inches is always an opportunity for math error, especially figuring things in your head. One observation I’ve noticed in the field is that most trades on construction sites only use inches and not feet. For example, one carpenter measuring for the next piece to be cut by another carpenter calls out “63 and 3/8 ths” not “5 foot 3 and 3/8 ths.”


Even if you mark the stud with a pencil for your colleagues, you need to communicate (left side, heart or right side of the mark) and anticipate if not listening…

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We could use the one dollar = 6" ruler.

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We called it 53 and 3. We assumed eights.

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Oh, right. And sometimes followed by “heavy” or “light” to add a little more nuance to the measure.

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Or “Strong” / "Light, and “Plus” / “Minus”. The pitch of the preceding “Ah” determines whether the strong/light is an eighth or a sixteenth.

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In September of 1999, after almost 10 months of travel to Mars, the Mars Climate Orbiter burned and broke into pieces. On a day when NASA engineers were expecting to celebrate, the ground reality turned out to be completely different, all because someone failed to use the right units, i.e., the metric units!

How NASA Lost a Spacecraft From a Metric Math Mistake | SimScale!


I cannot upload in New Zealand!

Or in Australia.

You mean watch the YouTube video?


Yes but maybe I will use my VPN :slight_smile:

That’s what I wondered. When my sister shot a movie in Poland, and there was publicity on Polish TV, I couldn’t watch it here in the US with a similar message. Not speaking Polish, however, I guess I wouldn’t get much out of it.

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Viewed now. Very good. Did make me laugh out loud.

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