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.
> 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?
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)
> calling spelling I'd never see a "common mistake" (like "gr." for grams)
Maybe I should change the example for gram to "gm" (or "GM"), because I actually see that in Canadian supermarkets - on the price label on shelves, not on the product label.
> I saw "Set the oven to 450 K", and I realized that the examples are to be taken with a grain of salt
I mean, that example exists to reinforce why we should continue using degrees Celsius for everyday temperatures. I'm simultaneously describing what we should do and what we should not do. The statement is less impactful if I only describe the positive example without the negative.
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.
> Although still widely used in physics and chemistry, the angstrom is not officially a part of the International System of Units (SI). Up to 2019, it was listed as a compatible unit by both the International Bureau of Weights and Measures (BIPM) and the US National Institute of Standards and Technology (NIST). However, it is not mentioned in the 9th edition of the official SI standard, the "BIPM Brochure" (2019)[13] or in the NIST version of the same,[14] and BIPM officially discourages its use. The angstrom is also not included in the European Union's catalogue of units of measure that may be used within its internal market.
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!
> nice to know the risks of making each of these mistakes ... only found a few places where a mistake can have real negative consequences ... context is king
That's an excellent question. As an analogy, I would say that it's similar (but not identical) to making mistakes in natural-language spelling and grammar.
For many cases, you are correct that the meaning can be repaired with context. dis iz da kase 2 wif nglish, as u kan sea w/ this sntnce.
Likewise, there will be some cases where a single letter or word can make all the difference. "He hit her" conveys a different meaning than "He hit on her"; an ESL student might only learn the verb and not the important subsequent preposition. And then there are pronunciations: https://www.youtube.com/watch?v=3Q44_A4NzjI .
Finally, by excusing the writer of all their mistakes, it puts the onus on the reader to grasp the right meaning. And if causes the reader to be confused or misunderstand, the reader has to go back and ask questions. That's a selfish shifting of effort.
You might not appreciate this, but there are fields where mb meaning millibit actually matters. Look at information theory such as data compression and error correction codes. We might say that JPEG encodes each RGB pixel with 3.0 bits, and WebP uses 2.8 bits/pixel, so WebP is 200 millibits per pixel more efficient than JPEG. There are many codec competitions where improvements are in the range of millibits per symbol (though they're written rather normally as 0.123 bits to not scare people).
By "autocorrecting" "mb" to "megabyte(s)", we lose out on the ability to express "millibit(s)".
> literally nobody speaks in terms of gigameters or teragrams or whatever
So why do we use megabytes, gigahertz, megapascals (for some industrial chemical processes), megawatts (power plants)? It's just a matter of habit. We collectively decided that kilometre is the biggest unit we'll tolerate, even though there is nothing technically wrong with megametre, gigametre, etc. We have the same problem with avoiding megagrams, kilolitres, kiloseconds, etc.
> 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.
That's nice, and it is true that when drawing attention to a comparison, the same unit should be used (Pat Naughtin and The Metric Maven both advocate for this idea). But it's also okay to write that the moon is 400 Mm away in the context of astronomy, because very few distances between bodies in space are less than 1 Mm.
The big problem with how writers treat the kilometre is that we always end up with things like "the nearest star is 4.35 light-years or 40 trillion km away". Instead of using SI prefixes as designed, we end up jamming big number words in front of the unit, and that doesn't make things any clearer. Would you like it if I said my CPU is 3.5 billion hertz, and ban all the mega-, giga-, etc.? I could even make the case that this isn't theoretical, because for example my monitor runs at 60 Hz, and we certainly must not call it 0.000 000 06 GHz with any sense of normalcy.
> My car weighs roughly 1 ton, so Hafthor's 501kg deadlift record is half my car
And you contradicted yourself because now you're using different units. It would be better to say that your car is 1000 kg and the deadlift record is 501 kg. So it's like sometimes you accept changing units, sometimes you don't.
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...
> good luck with that... electrical power engineering speaks in kWh not MJ
Then it's industry-specific jargon. Note that some places bill your natural gas consumption in megajoules. Food energy is quoted in kilojoules in SI, or calorie/Calorie/kilocalorie otherwise.
The problem is that if you want to make any comparisons, you need to use the same units.
An athlete eats 100 Calories, gets on an exercise bike, and powers a 100-watt light bulb for 3000 seconds. What is her thermodynamic efficiency?
To make the 500 km journey, the old car consumed 1 GJ worth of heat energy in gasoline. The new electric car consumed 300 kW⋅h. Which one consumed less energy?
> Particle physicists will hate you if you take electron volts from them
I can understand why they love their traditional unit of measurement.
The problem is that their unit measures the same type of quantity (energy) as an existing SI unit - the joule.
We've seen this play out in countless industries already, where they have their own specific units and refuse to interoperate.
Heating in BTUs, cooling in tons, explosions in kilotons of TNT, barrels of oil.
Astronomy in light-years or parsecs or astronomical units, typesetting in points, football in yards (instead of feet), microscopic things constantly compared to the width of a human hair, ~5 different scales of shoe sizes across the world.
> 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
I agree with this rule. I guess if you write it out in words, it would be:
Readit News
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 :)
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 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)
Maybe I should change the example for gram to "gm" (or "GM"), because I actually see that in Canadian supermarkets - on the price label on shelves, not on the product label.
> I saw "Set the oven to 450 K", and I realized that the examples are to be taken with a grain of salt
I mean, that example exists to reinforce why we should continue using degrees Celsius for everyday temperatures. I'm simultaneously describing what we should do and what we should not do. The statement is less impactful if I only describe the positive example without the negative.
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.
I'm sure it's just a typo, but 15,000 grams is 15 kilograms. So: 15.07 kg.
I don't think they arrived at some of the more extreme examples by accident, but I could only speculate on the intent behind them.
But standard is kB, from kilo prefix.
In Germany you will sometimes see Qm for "Quadratmeter" (m²).
(Kernel Virtual Machine in Linux or Keyboard Video Monitor in server switching kit)
If anything, I would've expected phone keyboards to turn m2 into m².
-- https://en.wikipedia.org/wiki/Cubic_centimetre
> Although still widely used in physics and chemistry, the angstrom is not officially a part of the International System of Units (SI). Up to 2019, it was listed as a compatible unit by both the International Bureau of Weights and Measures (BIPM) and the US National Institute of Standards and Technology (NIST). However, it is not mentioned in the 9th edition of the official SI standard, the "BIPM Brochure" (2019)[13] or in the NIST version of the same,[14] and BIPM officially discourages its use. The angstrom is also not included in the European Union's catalogue of units of measure that may be used within its internal market.
-- https://en.wikipedia.org/wiki/Angstrom#Current_status
/s
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!
That's an excellent question. As an analogy, I would say that it's similar (but not identical) to making mistakes in natural-language spelling and grammar.
For many cases, you are correct that the meaning can be repaired with context. dis iz da kase 2 wif nglish, as u kan sea w/ this sntnce.
Likewise, there will be some cases where a single letter or word can make all the difference. "He hit her" conveys a different meaning than "He hit on her"; an ESL student might only learn the verb and not the important subsequent preposition. And then there are pronunciations: https://www.youtube.com/watch?v=3Q44_A4NzjI .
Finally, by excusing the writer of all their mistakes, it puts the onus on the reader to grasp the right meaning. And if causes the reader to be confused or misunderstand, the reader has to go back and ask questions. That's a selfish shifting of effort.
> email me a 15mb (millibar) document
It looks like the symbol for bar (unit) is "bar", not "b". It is not part of SI. https://en.wikipedia.org/wiki/Bar_(unit)
You might not appreciate this, but there are fields where mb meaning millibit actually matters. Look at information theory such as data compression and error correction codes. We might say that JPEG encodes each RGB pixel with 3.0 bits, and WebP uses 2.8 bits/pixel, so WebP is 200 millibits per pixel more efficient than JPEG. There are many codec competitions where improvements are in the range of millibits per symbol (though they're written rather normally as 0.123 bits to not scare people).
By "autocorrecting" "mb" to "megabyte(s)", we lose out on the ability to express "millibit(s)".
> literally nobody speaks in terms of gigameters or teragrams or whatever
So why do we use megabytes, gigahertz, megapascals (for some industrial chemical processes), megawatts (power plants)? It's just a matter of habit. We collectively decided that kilometre is the biggest unit we'll tolerate, even though there is nothing technically wrong with megametre, gigametre, etc. We have the same problem with avoiding megagrams, kilolitres, kiloseconds, etc.
> 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.
That's nice, and it is true that when drawing attention to a comparison, the same unit should be used (Pat Naughtin and The Metric Maven both advocate for this idea). But it's also okay to write that the moon is 400 Mm away in the context of astronomy, because very few distances between bodies in space are less than 1 Mm.
The big problem with how writers treat the kilometre is that we always end up with things like "the nearest star is 4.35 light-years or 40 trillion km away". Instead of using SI prefixes as designed, we end up jamming big number words in front of the unit, and that doesn't make things any clearer. Would you like it if I said my CPU is 3.5 billion hertz, and ban all the mega-, giga-, etc.? I could even make the case that this isn't theoretical, because for example my monitor runs at 60 Hz, and we certainly must not call it 0.000 000 06 GHz with any sense of normalcy.
> My car weighs roughly 1 ton, so Hafthor's 501kg deadlift record is half my car
And you contradicted yourself because now you're using different units. It would be better to say that your car is 1000 kg and the deadlift record is 501 kg. So it's like sometimes you accept changing units, sometimes you don't.
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."
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.
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").
> 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."
https://physics.nist.gov/cuu/pdf/sp811.pdf
Yeah... all of my spectrum analyzers, signal generators, software-defined radios, antennas and RF interface control documentation is not ISO/IEC compliant...
Then it's industry-specific jargon. Note that some places bill your natural gas consumption in megajoules. Food energy is quoted in kilojoules in SI, or calorie/Calorie/kilocalorie otherwise.
The problem is that if you want to make any comparisons, you need to use the same units.
An athlete eats 100 Calories, gets on an exercise bike, and powers a 100-watt light bulb for 3000 seconds. What is her thermodynamic efficiency?
To make the 500 km journey, the old car consumed 1 GJ worth of heat energy in gasoline. The new electric car consumed 300 kW⋅h. Which one consumed less energy?
> Particle physicists will hate you if you take electron volts from them
I can understand why they love their traditional unit of measurement.
The problem is that their unit measures the same type of quantity (energy) as an existing SI unit - the joule.
We've seen this play out in countless industries already, where they have their own specific units and refuse to interoperate.
Heating in BTUs, cooling in tons, explosions in kilotons of TNT, barrels of oil.
Astronomy in light-years or parsecs or astronomical units, typesetting in points, football in yards (instead of feet), microscopic things constantly compared to the width of a human hair, ~5 different scales of shoe sizes across the world.
> 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
I agree with this rule. I guess if you write it out in words, it would be:
* Incorrect: "Power: 480 volt-amps-reactive (VAR)"
* Correct: "Power (reactive): 480 volt-amps (V⋅A)"
* Correct: "Reactive power: 480 volt-amps (V⋅A)"
By the way, you can link to a specific page like this: https://physics.nist.gov/cuu/pdf/sp811.pdf#page=16