When we talk about measurement units here at the National Institute of Standards and Technology (NIST), you’ll typically hear us rattling off the official ones — such as the meter, the second and the kilogram. These official measurements, which are part of the International System of Units (SI), have evolved from quantities that people mostly defined with their bodies and everyday items to more universal measures that even an extraterrestrial could readily understand — and may even be using (assuming they exist and have an institution like NIST).
But as much as we love the SI, today we’ve decided to share with you some of the many quirky (and decidedly nonstandard) measurement units that humans have invented throughout the ages.
At the dawn of recorded history, the Egyptians and other ancient cultures based the cubit on the distance from the elbow to the end of the middle finger. A Roman mile equaled 1,000 paces that Imperial soldiers would march together in formation. Each pace was approximately 5 feet, and therein lies the problem: The distances were approximate. In medieval times, English traders disputed the exact length of the yard, but as legend has it, King Henry I of England (who ruled from 1100-1135) settled the issue by defining the yard as the distance from the tip of his nose to his extended arm. On more solid historical ground (but still shaky measurement science ground), King Edward II of England declared in 1324 that the inch was the length of three grains of barley arranged end to end (thereby begging the question, “Which three grains?”).
Students of U.S. history have likely heard of a score, or 20 years, as in Abraham Lincoln’s “Four score and seven years ago” line in the Gettysburg Address, but do you know where the term comes from? It’s from the Old Norse word “skor” meaning notch. The score is believed to originate from the practice of counting cattle or sheep; a farmer would put a mark on a stick after counting each group of 20. (While the unit itself may not be as quirky as others, we’ve included it because we thought at least its origin story wouldn’t put you to sleep.)
While we’re on the subject of agriculture, the cow-calf unit estimates the amount of land that is needed to provide food (in the form of grass and other plants) for a beef cow with a calf at its feet. Still used today in various forms, it’s meant to compare the food requirements for different types of livestock such as goats (typically an eighth of a cow-calf unit), pigs (one-fourth) and alpacas (one-tenth).
In trade, it’s important to have measurement units for a product’s weight, or more precisely, as we know today, its mass. An object’s weight depends on the strength of gravity at wherever it’s located, but its mass is the same anywhere, whether it’s on Earth, Mars or in orbit.
Before superheroes, before comic books, even before most of recorded history, there was the batman — not the Dark Knight of today, but a unit of mass that originated in the ancient city of Babylon (near what is today Baghdad, Iraq) that is equivalent to 7.7 kilograms or 16.7 pounds. The batman was used for trade well into the Middle Ages.
Quirky measurement units didn’t go away in modern times. Physics students still learn about the slug, a unit of mass in the U.S. customary and British Imperial systems of units. It’s a decidedly less elegant-sounding counterpart to the metric system’s kilogram. In case you’re wondering, the term originally referred to a slab of metal, not a little slimy creature, evidenced by the fact that one slug is equal to about 15 kilograms.
Perhaps the enterprise with the greatest number of quirky units is the measurement of alcoholic beverages. The effects of these beverages notwithstanding, it’s likely you’ll briefly forget about the liter or fluid ounce when you hear about the butt. Moreover, you may not think you’re hearing things correctly when you learn the butt is the equivalent of two hogsheads. In the U.S., one butt is equal to 126 gallons (so a hogshead is equal to 63 gallons).
If you’d like to cleanse your palate after all this and sound a bit more sophisticated, you can name-drop the international bitterness unit (IBU) scale to your beer-loving friends. One IBU is equal to a part per million of an acid in hops known as isohumulone that gives beer its bitter taste (above 45 IBU is pretty hoppy). A noggin (or gill) was first used to describe a quarter pint and later a half pint. The ale gallon, which Queen Elizabeth I of England established but is no longer used today, is equal to about 1.22 gallons (to account for all the foam that comes out from the tap, perhaps?).
Some people use air quotes, and others play air guitar, but did you know that vacuum manufacturers sometimes use the air watt? Developed by the standards organization ASTM International, it essentially expresses a vacuum’s suction power in terms of its airflow rate and suction pressure. It’s different from the ordinary electrical watt that is used to describe the power of a lightbulb or hairdryer.
A fictitious year may sound like a period of time we want to pretend never happened (or an entire season of the soap opera Dallas that its producers wanted us to forget), but it actually describes the amount of time it takes an ideal version of Earth to revolve around an ideal Sun. No longer used, its purpose was to accurately mark the time at which certain astronomical events would occur (such as the position of a star in the sky) while ignoring irregularities in the Earth’s orbit.
Quirky units continued to spawn in the digital age. In computing, engineers came up with the nibble (four bits of information) and the crumb (two bits), building upon the wordplay that began with the byte (eight bits). When naming the byte, its creator Werner Buchholz spelled the term with a “y” and added an “e” all to avoid confusion with the single bit.
You might think it’s related to vaping, or a magic dragon, but a puff is an informal name for a picofarad (pF), which describes an object’s ability to hold electrical charge. Engineers sometimes use the term jerk to describe the rate at which acceleration changes; it sounds like a natural unit to use when designing roller coasters.
The parsec is not a quirky unit per se, but it got put to quirky use in the original 1977 “Star Wars” movie when Han Solo boasted that he “made the Kessel Run in less than 12 parsecs.” The problem is that the parsec is not a unit of time but distance. We might want to blame the Imperial Academy that Han briefly attended for miseducation, but the problem was nonetheless solved onscreen in the 2018 prequel film Solo: A Star Wars Story. As it turns out, Han navigated the famous spice-smuggling route by using black holes whose space-time distortions reduced the route’s usual distance from 20 to 12 parsecs. We don’t know another example of retconning a scientific measurement unit so that it’s used properly in a movie, but we sure do appreciate it!
In addition to being fun, quirky units demonstrate how important measurement has been throughout the entire history of our species. They provided a (somewhat) common language that people used to describe how big something was and how much something weighed, so that two traders could agree on a fair purchase price, for example. They became problematic when they varied from place to place, or person to person. In contrast, today’s units depend on unchanging constants of nature, such as the speed of light. Unlike someone’s forearm or butt, it’s something everyone in the world — and hopefully even an extraterrestrial — could agree on.
You can find many more quirky measurement units online, including two of the sources that I used to compile this blog post: How Many? A Dictionary of Units of Measurement (compiled by Russ Rowlett, a retired professor at the University of North Carolina) and the Oxford Dictionary of Weights, Measures, and Units. And if you’d like to take a break from the quirkiness, and learn about how today’s scientific measurement units were recently updated to all be the same everywhere in the world, and even the universe, check out the NIST site on the SI Redefinition.