You’re standing in the grocery store, staring at a bag of apples. The label says 5 lbs. It’s one of those weird things we just accept as kids, like why "colonel" is pronounced with an "r" or why we drive on parkways and park on driveways. But if you actually stop to think about it, why the abbreviation of pounds is lbs makes absolutely zero sense in English. There isn't an "L" or a "B" anywhere in the word "pound."
It’s annoying. It's confusing. Honestly, it’s a bit of a linguistic mess left over from a dead empire.
Most of our weirdest measurements come from the Romans. They loved order, but they also left us with a legacy of abbreviations that require a history degree to decode. To understand the "lbs" situation, you have to look back about 2,000 years to a phrase that sounds like a Harry Potter spell: libra pondo.
The Roman Connection: Libra Pondo
The word "pound" actually comes from the second half of that Latin phrase, pondo, which basically means "by weight." However, the unit itself was the libra.
If you’ve ever looked at a horoscope or seen the scales of justice, you know Libra is the sign of the scales. It represents balance. For a Roman merchant, a libra was a specific weight—roughly 328 grams, though it fluctuated depending on who was doing the weighing and which emperor was currently in power.
So, when they weighed out grain or silver, they called it libra pondo. Over time, English speakers decided to keep the word "pondo" (which evolved into "pound") but they kept the abbreviation for "libra" (which became "lb"). It’s a total linguistic split-brain scenario. We took the name from one word and the shorthand from another.
Imagine if we started calling "gallons" by the name "water" but abbreviated it as "gl." That’s essentially what happened here.
Why the 's' at the end?
This is where it gets even more inconsistent. In strict Latin, you wouldn't necessarily just slap an "s" on the end to make it plural. But English is a scavenger language. We steal words from everywhere and then try to force them to follow our rules. Since we add an "s" to make "pounds" plural, we naturally started adding an "s" to "lb."
Technically, many style guides—especially in scientific or technical writing—will tell you that "lb" is both singular and plural. One lb, ten lb. But in common usage, "lbs" won. It feels more "right" to the English-speaking brain, even if it’s technically a double-pluralization of a Latin root.
The "lb" with a Bar: The Origin of the Hash Symbol
While we're talking about why the abbreviation of pounds is lbs, we have to talk about the # symbol. You call it a hashtag. Older people call it a pound sign. Musicians call it a sharp.
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But it started as a "lb."
Back in the day, when scribes were writing "lb" over and over again, they started getting lazy. They began connecting the two letters with a horizontal line across the top—a "tittle" or a bar—to show that the letters were linked together as a single unit of measurement. This was a common practice in medieval manuscripts to signify an abbreviation.
Over decades of fast handwriting, that barred "lb" morphed. The "l" and the "b" became vertical strokes, and the bar across the top became the two horizontal strokes.
Eventually, you got the #.
Next time you're tagging something on Instagram, remember you're literally typing a 14th-century shorthand for a Roman libra. It’s a direct evolution from the same root that gave us the weight of a steak.
Different Kinds of Pounds
Not all pounds are created equal. This is where things get genuinely messy for people in science or international trade.
In the United States, we mostly use the avoirdupois pound. That’s the standard 16-ounce pound used for groceries, body weight, and shipping. It’s the one everyone is thinking of when they ask why the abbreviation of pounds is lbs.
But then there’s the Troy pound.
If you’re buying gold, silver, or gemstones, you aren't using the same "lbs" you use for flour. A Troy pound is only 12 ounces. Even crazier? A Troy ounce is actually heavier than an avoirdupois ounce, but the Troy pound is lighter than the standard pound. It’s a nightmare.
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- Avoirdupois Pound: 453.59 grams (Standard stuff)
- Troy Pound: 373.24 grams (Precious metals)
- Tower Pound: An old British unit used for coinage before the 1500s.
The reason "lb" stuck across all these versions is that they all theoretically traced their ancestry back to that original Roman libra. Whether you were weighing gold in London or grain in Rome, the "lb" was the universal shorthand for "this is the weight of this thing on a scale."
The Lira and the £ Sign
If you’ve ever wondered why the British currency (the Pound Sterling) uses a fancy "L" symbol (£), it’s the exact same story.
Originally, a British pound was literally worth one pound of high-quality silver. Because the Latin word was libra, they used a stylized "L" to represent their currency.
It’s all the same root.
- The lb on your scale.
- The £ in a London bank.
- The Lira, which was the currency in Italy before the Euro.
They are all just different ways of saying "libra." The Romans really did a number on our systems of measurement. Even after the empire collapsed, the sheer convenience of their trade routes and bookkeeping meant that everyone from the Italians to the Brits kept the terminology. It was the "USD" of the ancient world.
The Weirdness of the United States
We are one of the very few countries still clinging to the "lb." Most of the world has moved on to the kilogram.
The kilogram is part of the metric system, which was designed during the French Revolution to get rid of all this confusing Roman nonsense. Instead of 16 ounces to a pound and 12 inches to a foot, they wanted everything based on tens. It’s logical. It’s clean.
But the "lb" has staying power. There’s something tactile about it. In the US, the Imperial system is deeply baked into our manufacturing, our recipes, and our sense of self. We know what a 5 lb dumbbell feels like. We know what a quarter-pounder looks like.
Switching would mean changing every road sign, every cookbook, and every scale in the country. It’s a multi-billion dollar headache that nobody wants to deal with. So, the "lb" stays.
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Does the "s" actually matter?
If you're writing a formal paper or working in a lab, you should probably stick to "lb" for both singular and plural. It’s the "correct" way to do it according to the National Institute of Standards and Technology (NIST). They argue that abbreviations for units shouldn't have an "s" because the "s" can sometimes be confused with "seconds."
However, if you're writing a blog post or a grocery list, "lbs" is perfectly fine. Everyone knows what you mean. The "s" has been used for hundreds of years. In fact, you can find "lbs" in books dating back to the 1700s. Language isn't just about what is technically correct in a dictionary; it's about how people actually communicate.
Actionable Insights for Using Weights and Measures
Since you're clearly interested in the nuances of weight abbreviations, here are a few practical things to keep in mind for everyday life:
1. Watch your labels in the UK
In the UK, you’ll often see prices per kilogram, but people still talk about their body weight in "stones." One stone is 14 lbs. If someone says they weigh "10 stone," they’re about 140 pounds. Don't let it throw you off.
2. The "p" is silent, the "lb" is weird
When typing, the # symbol is officially the "octothorpe." If you want to sound like a genius at a dinner party, tell people the # symbol is a barred "lb" that got messy over time. It’s a great piece of trivia.
3. International Shipping
If you are shipping something internationally, always use kilograms. Even though we love our "lbs," the rest of the world’s customs forms and logistics software are built on the metric system. Using "lbs" on an international package can sometimes lead to rounding errors that cost you extra money.
4. Baking Precision
If you’re following a recipe that uses "lbs" and "oz," consider getting a digital scale that toggles between metric and imperial. Most professional bakers actually prefer grams because a "pound" of flour can change volume depending on how humid it is or how much you packed the measuring cup.
The story of "lb" is a perfect example of how history never really goes away. It just hides in plain sight, tucked into our grocery stores and gym equipment. We are still using the shorthand of Roman merchants from 2,000 years ago, and honestly, that’s kind of cool.
How to Correctly Use the Abbreviation Today
When you’re writing, just remember the context.
- Scientific/Formal: Use lb (e.g., "The sample weighed 5 lb.")
- Casual/Marketing: Use lbs (e.g., "Lose 10 lbs in two weeks!")
- Currency: Use £ (Never use "lb" for money unless you're talking about the physical weight of silver coins).
By understanding why the abbreviation of pounds is lbs, you aren't just memorizing a weird fact—you're seeing the "source code" of the English language. It’s a mess of Latin, French, and old-school English stubbornness, and it’s likely not going anywhere anytime soon.