I was surprised to see "L" as the "only correct" (though as minor mistake) abbreviation for a liter, being certain "l" or "ℓ" is the way to go, as that's how I was taught so far. Turns out that SI actually allows both "l" and "L", but I would only ever use the uppercase if it's a sans-serif font in a non-prefixed unit ("L" as opposed to "ml"). I've never seen any can or bottle using "mL" or "cL".
Some of the examples go pretty far too, either calling spelling I'd never see a "common mistake" (like "gr." for grams), or by being too scientifically correct for a casual usage, for example in a press article ("(100 + 200) grams", right).
But then I saw "Set the oven to 450 K", and I realized that the examples are to be taken with a grain of salt :)
In ex-Yugoslavia countries using gr (usually without a dot) for grams used to be a fairly common thing. Last few decades as EU standardization takes place it's a lot rarer to see. Also in Croatia in everyday life people will far more often use decagrams (10g), shorten colloquially as 'deka', than grams - which leads to even more confusion because the SI abbreviation for decagrams is dag, not dg (which is decigram, 0.1g), and it's often mixed - even some primary school books had these typos.
"Grains" are still used for measuring out powder/chemicals (also arrows). If I saw "gr", I'd interpret that as grains rather than grammes as "g" is definitely grammes, so the extra "r" must signify something.
> either calling spelling I'd never see a "common mistake" (like "gr." for grams)
Almost all cooking books I have do this (sample size is not big though, and with almost all I mean all except one). I don't know why though, maybe it's an old abbreviation which stuck in certain text types?
I've got a serious bugbear with recipes using "cups" as a measure - it infuriates me. Who in their right mind uses a volume measurement for foods that can vary hugely in their size according to how long they've been sitting around?
The vast majority of home cooking in the US measures in cups. Certainly there are people in-the-know who are going to be more precise and measure by weight, and most restaurant kitchens will probably do so as well.
I agree it's not great, but ultimately I've found it doesn't really matter in practice, even for baking most of the time. For regular cooking I do get frustrated when I'm asked to include "2 cups of shredded chicken" or the like, but ultimately it really doesn't matter. Being off won't ruin the recipe, and often more or less of a particular ingredient is a matter of personal taste anyway.
I have a kitchen scale, but it's always simpler and easier to grab and use a measuring cup, so that's what I do most of the time, unless the recipe actually calls for weight without giving volume.
I just don't get it - surely homes in the U.S. also have measuring scales? Outside of the U.S., we just go for measuring ingredients by weight which completely gets around the issue of settled ingredients or the inconsistency of measuring things by volume. Why can't recipes just use metric measurements (I'll allow the substitution of grammes for weight rather than newtons) and also provide the quick'n'easy and inaccurate cups measures too?
On the capital L for litre, that’s a suggested rule (second table), not mandatory.
I also agree though, there are things there which are decidedly not mistakes (e.g. “mcg”, which is most commonly used to avoid confusion between a sloppily written mu and a sloppily written m. I’ve seen this most commonly in handwriting by doctors and vets)
Lots of these are country dependent in terms of what is familiar to people. To some degree that matters if your primary communication is not international but domestic.
For e.g. in the UK sqm is very common, particularly when looking at property. On RightMove which is the most popular property website here, for e.g. you can see here that the default is `sq ft` with `sq m` given underneath: https://www.rightmove.co.uk/properties/140100683#/?channel=C...
In terms of things like mixture of units, I appreciate you want to give in one unit but I think the things chosen are a bit strange. I've never seen anyone write '15070 grams', it'd almost always be given as 1.507 kilograms.
Right, the uppercase conventionally means 1024 so it should be kB or ko for 1000.
There are some odd rules, like L for liter because of readability or some other reason. I've also learned in (French) school that we shouldn't use kL, that it doesn't exist. It does exist, but we apparently don't want to use it and use hL instead. Some people thing it's a linear unit and not a cubic unit. We count liters like we count potatoes and we use m3 for volume math.
It would have been nice to know the risks of making each of these mistakes, since honestly I only found a few places where a mistake can have real negative consequences.
As with all things, context is king. I'm not going to be confused when my colleague asks me on slack if it's OK to email me a 15mb (millibar) document - I know what they meant. Nor am I going to worry if it's actually MiB vs MB, in this context it does not matter.
Also, although it probably be nice that we all standardised on the correct prefixes, literally nobody speaks in terms of gigameters or teragrams or whatever. We carry with us an internalisation of real world measurements, and use that to compute relativity when we read/hear these numbers. It's roughly 1000km from my home town to the coast, so if if the moon is roughly 400,000 km away, then that's 400x the distance, pretty far. My car weighs roughly 1 ton, so Hafthor's 501kg deadlift record is half my car - pretty impressive!
The most common error I see is "kph" which doesn't even have any possible meaning. 'kilos per hour' would in most places be taken as "kilograms per hour". As in "my weight increases by 3 kph when I visit McDonalds"
Not defending 'kph' exactly, but I can see how some native metric speakers (in Australia at least) might arrive at that solution on their own.
You're right about 'kilos per hour': 'kilos' will always be taken to mean kg.
But in speech, 'kays' is a common abbreviation for both km and km/h (confusingly).
So 'kph' would be an ambiguous way of writing 'kays per hour'.
I have heard a small number of people say K.P.H. as an initialism.
kays (distance) e.g. "Thongs'll do, we're only walking a few kays down the road."
kays (speed) e.g. "Apparently he was doing 120 kays in the Barina. I'll miss him."
kph seems to come from people that normally work in miles but switched to metric for one reason or another. The common notation I almost always see for kilometres per hour would be km/h, in rare occasions with `h` exchange for whatever letter the local translation of "hour" starts with.
I don't think anyone would confuse kph for kilograms per hour (after all, that would be kgph or kg/h, and I don't think I've ever had to calculate kilograms over time outside high school anyway). Usually, context clues make it pretty clear what's being described.
There's no confusion, the problem is simply that seeing "kph" automatically expands to "kilos per hour" in non- native English brains. That's overridden by logic, obviously, but that jarring effect is always there.
kph doesn't bother me, but I'm American, and we're pretty sad and pathetic when it comes to metric, and it's similar enough to how "mph" is used here that it immediately makes sense.
What makes your specific comment funny is that we're talking about different usage of things in different languages and countries, and in one sentence you managed to express frustration at how other people say things incorrectly, while using an English idiom incorrectly. It's "drives me up the wall" (singular "wall").
> Use 1008 MJ monthly electrical energy consumption instead of 280 kW⋅h monthly electrical energy consumption
> Avoid common non-SI units (suggested)... For serious science and engineering, SI units like metres per second should be used instead.
Yeah good luck with that... electrical power engineering speaks in kWh not MJ
> 150 pJ gamma ray instead of 938 MeV gamma ray
Particle physicists will hate you if you take electron volts from them
While I'm at it, do you know that attaching suffix to SI unit is not allowed by SI / IEC /ISO? So abbreviating megawatt of thermal energy as MWth or decibel referred to 1 milliwatt of power as dBm is technically illegal:
> "When one gives the value of a quantity, it is incorrect to attach letters or other symbols to the unit in order to provide information about the quantity or its conditions of measurement. Instead, the letters or other symbols should be attached to the quantity."
Yeah... all of my spectrum analyzers, signal generators, software-defined radios, antennas and RF interface control documentation is not ISO/IEC compliant...
- "Fuel consumption of 9.4 L / 100 km" is not "the right form" is a modern take, a more classic and still valid SI one is km/l which is very similar to "Fuel consumption of 9.4 LPK";
- "25 {kW/h,kW⋅h} to boil a tank of water" are both strange forms, kWh is the common accepted way to express energy, no center dot multiplication needed;
- multiple prefix (vs power-of-10) and bare prefix are as well commonly accepted, I see no reasons to consider them wrong, while I can state formally wrong "2 kilograms of rice" because we do not measure the mass but the weight so it should be 1.961daN where deca-newtons are commonly used because 1 daN is roughly 1kgf commonly shortened to 1kg as we can commoly count 1kg[f] == 1 daN... For instance climbing equipment in the EU use daN to express maximum loads of connectors, ropes etc because of that;
- multiple quantities much depend on industry and conciseness, as we do not write units in table values but only in headers we tend not to write them three times in a row where from the context is clear what numbers means.
The biggest issue is makes habits changes. Actually we should not use km/h as well, since for SI base unites are m/s, but 3.6 is not an easy conversion like kgf/daN, so in the EU we keep using km/h, something meaningful in the past, when we go by horses and feet, but not much needed today.
Not to count software, where often recognize "°C" (two chars) BUT not ℃ (U+2103) and so on.
I really appreciate this kind of plain and simple writeup, without getting into any "falsehoods programmers believe about metric"-type clickbait. Nice one.
Note: The official SI unit “liter” was written “l” until a couple of decades ago, when they changed it to “L” due to frequent legibility issues (l/I/1). Some old texts use the old convention.
I don’t know which field you work in, but I do research in physics and chemistry and L is the dominant convention in the papers I read. I also teach intro physics at the university level and the textbook uses L.
In high school (~2008) we were taught that this was the correct new abbreviation for liter in chemistry, but I remember that at the time lower-case l (or sometimes \ell) was still normal as well. These days, I rarely see that.
(Off-topic: “Small caps” is not the same as “lower case”.)
After I read your comment and went into the kitchen and the first thing I saw was a handsoap bottle what had "1 L" written on it. Weirdly the milk had "1 ltr" on it :S
So, when using the kelvin temperature scale, it's lower case when using "kelvin", but uppercase when using the abbreviation "K"? That annoys me as kelvin is a name and even my phone wants to capitalise it.
I've always assumed "giga" is capitalised because it one might confuse a lower case g for "grams". Technically, 1gm is one gram-meter (grams * metres), whereas 1Gm is a thousand kilometres. You don't often encounter weird combined units like gram-metres outside of physics, except maybe for kWh (kW * 1 hour), but I don't see why you wouldn't be nice to physicists and give them the extra clarity.
Other order of magnitude indicators are capitalised to distinguish them from their smaller counterparts (millimetre/Megametre).
Wikipedia states that the distinction is because units named after a person always start with a capital letter. I've always assumed Hz has to be capitalised to prevent confusion with the hecto prefix (hHz being 100Hz). I don't think there's a unit or order of magnitude that's abbreviated to `z`, so in theory "Hz" could just be "H",
I think Hz is more readable, but that's probably because I'm used to it.
I had structural engineering and electronics in school and especially when you get compound units like Nm (newton meters) not wondering if the N is a newton or the SI-prefix nano is not nothing.
In the end the reason for the weird capitalization is just to avoid situations where that ambiguity will occur.
I remember me and a friend asking our physics teacher if it wasn't a problem that tera (T) and tesla (T) were the same symbol. He looked at us, paused a bit, then explained how absolutely enormous a terra tesla would be, and thus why that isn't actually an issue :P
I disagree with that rule. I get that people spell liter, gram, meter in lower case, but units based on names of historic persons like Volt, Ampere, Coulomb, Pascal and Kelvin deserve to be capitalized.
The unit symbols for those units (A, C, P and K) are capitalized, but the units when spelled out (ampere, coulomb, pascal and kelvin) are not, just like the spelled out forms of liter, gram and meter.
Capitalisation isn't universal. Languages like German capitalise every noun, so from a German perspective, Gram, Metre, and Litre should all be capitalised and it's the English that are wrong for using lowercase units.
Meanwhile, English capitalises stuff that other languages don't, like the names of languages, times (days and such), and for some reason "I". By the time the metric system was conceived, English still capitalised most nouns (just look at the US constitution for example) after very recently coming into contact with the concept of capital letters in the first place, something copied from German printing presses.
And then there are the many languages that don't even have capitals, which will probably question why there are two ways to write every letter when they first learn languages with a Latin alphabet.
Nothing "deserves" to be capitalised, every language just decided to stick to some arbitrary rules. There's no good reason why `Monday` is more important than `website`, or why `I` is more important than `you`.
This list strikes me as overly nitpicky. Certainly some of the bad example usage is a problem (e.g. mb vs. MB means two very different things, millibit vs. megabyte), but so much of this in practice just really doesn't matter.
Sure, if I'm doing a bit of formal writing, I'm going to do things correctly. But I don't see it as a problem for people to use odd abbreviations like "mtrs" or incorrectly pluralize as "kms" in informal writing. People will not have trouble knowing what you mean. No one is going to say things like "I drove 3 megameters over the past couple weeks". (Reading some of the longer explanations below seems to indicate that the author is not just talking about formal writing.)
And even in formal writing, a few of these are bit much, like good luck getting people to stop using electron-volts in favor of picojoules.
This just seems silly; it's hard to take this piece seriously, and all of the nitpicky arguments seriously undermine the (few) good arguments listed.
I thought this looked like good advice until I got to:
> Mass/weight distinction
> Incorrect: He weighs 70 kg; Correct: His mass is 70 kg
> Incorrect: She weighs 50 kg; Correct: She weighs 490 N on Earth
Really?! We’re not supposed to use kilograms to describe a person’s weight? And to describe someone’s weight, we have to use newtons and specify what planet they’re on? Good luck enforcing those rules.
There's a 5% range when converting mass into weight (depends on where on Earth you are). Santa loses a few kilos when he comes down to the equator. It's not enough for people to care, but it can be important if you're building something that needs to carry a lot of weight.
This is a very important distinction to make in scientific papers. Completely meaningless for most writing. If anything, physicists got the definition for the word "weight" wrong and patched up their mistake by adding the concept of "mass". Most mass is measured standing still on earth, so "weight" is fine unless you need to be precise.
> It's not enough for people to care, but it can be important if you're building something that needs to carry a lot of weight.
The problem is that the article presents these "corrections" without being clear what context they're important in. The examples given make it sound like the author is railing against people who use these forms in regular conversational speech. And even the longer explanations after the table still make it seem like the author isn't only concerned with formal/scientific writing.
So yes, in scientific papers, I do think this list is a reasonably good guide (though good luck getting particle physicists to give up electron-volts, or people writing about electrical power systems to give up kWh). But for everyday use it feels unnecessarily nitpicky.
For the specific mass vs. weight example, especially, regular conversation (spoken or written) is pretty much always going to use the term "weight", and using "mass" would feel stiff and unnatural.
The issue is that it's very common for people to use weight when they're referring to mass. We get away with it as our weight doesn't change very much when on Earth, but if we start populating other planets, then we're going to have to become more precise.
It's all pedantry. Physics makes a distinction between mass, a (mostly) invariant property of an object, and weight, the force proportional to your mass and the planet you're standing on divided by the square of the radius. Only physicists care about this distinction.
I would like to believe engineers care too. A simple action like standing up or being on a bus that's taking a curve will make items on your person weigh more.
Yeah, this is the only one that seems flat out wrong. When I'm on a bridge, I absolutely want to see "The bridge can hold up 3000 kg", NOT "The bridge can hold up 29 kN". Partly because "holding up" (as opposed to, say, withstanding) force sounds nonsensical, but primarily because knowing the maximum load in kg is much more useful.
You never know! Tomorrow that bridge might be on the moon, and how on earth (or how on the moon, indeed) will you know if it will hold up when you walk your herd of elephants over it!
I mean, that's still fine? The max load of that bridge on the moon will just be a different, higher value in kilograms. Since we don't move bridges between planets, it's fine to not advertise a universal value that applies everywhere.
Some of the examples go pretty far too, either calling spelling I'd never see a "common mistake" (like "gr." for grams), or by being too scientifically correct for a casual usage, for example in a press article ("(100 + 200) grams", right).
But then I saw "Set the oven to 450 K", and I realized that the examples are to be taken with a grain of salt :)
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