# Rant Of The Day: Units Of Measurement

Honestly, it’s the constant imperial / measurement changes that piss me off as a Brit.

Liquids are Metric unless it’s Milk or Beer (Which can and often are sold as both… in the same shop, you will find 1pt, 2pt, 4pt and 6pt milk right next to 0.5L, 1L and 2L bottles of pop. And you’ll see in some places 660ml beers being sold alongside 2 litre ciders)

Distances in Metres when it’s swimming pool length, running tracks & fields. Yard, Foot and Inches when it’s Height, Football, Snooker Cues, Carpets and pretty much anything else you can think of

Weight is Metric when it’s food, unless it’s a steak or a burger. Imperial when it’s a persons weight.

Car efficiency is measured in Miles Per Gallon, but the Fuel is sold in Litres.

Recipes for cooking food can and will contain both measurements as well as cups, which is even more confusing.

Trying aviation is just crazy (I used to fly occasionally from Cambridge to various places around the UK). Fuel uplift is in litres. Fuel gauges in kgs. Runway length in meters. Altitude in feet. Pressure in hectopascals. Wind & speed in knots …

I was trying to help my brother with some maths homework where they wanted him to poor different liquids into different container to see what was larger 1/2 pint or 330ml.

I had to explain to him why we used different measurement for liquids, it was impossible to explain besides its just how it is as we’ve never moved on.

The worksheet needed a measuring jug in both pints and mils and cups. I had to convert fluid ounces into pints so I could do that homework it’s stupid, as he’s six!

Honestly, I was nearly wanting to go metric!

## 66 thoughts on “Rant Of The Day: Units Of Measurement”

1. I think it is also a generational thing, peoples weight and heights are increasingly metric. Room or other dimensions and measurements would also be metric.

But wood and the like is of course sold as metric even if the measurements are suspiciously multiples of 30cm.

Long distances are of course miles, but I think many (younger) people just take a yard to be roughly a metre.

It is a mess, but lets just call it British quirkiness? Would you prefer to be American (something resembling Imperial but with a few mistakes) or European (fully metric)?

2. Go metric

3. The real problem with ‘metric’ is that it isn’t one system, but several. The UK signed up to the International System (which perversely is internationally known the French way round as SI). In many respects, this is brilliant, because in creates a unified system in which some of the ridiculousnesses of Imperial around work and energy have been sorted out – and I’m an Imperial fan. Most engineers are completely at home in SI, and understand the difference between mass and weight (force), but the public don’t, and hence weights in grammes and kilogrammes (when they are masses in SI). IN the older versions of metric g and kg ARE weights as well as masses.

Several problems arose because of the selection of SI, and in part, they are because other metricated countries use different versions of metric. Another problem arises because it isn’t really decimal, it counts in thousands. It used to annoy me beyond belief when kids came home from school measuring things in cm, when SI prefers mm and m.

A further problem with ‘metric’ is that the names are too long, and for domestic use the units aren’t all that useful, which is why the cm crept in. Mile, inch, pound, ton, foot, yard, stone, and so on are not only short and memorable, they relate to everyday quantities.

On the whole, however, some of the units are truly international by accident, in fact. A4 paper anyone (outside the US and Canada, of course).

4. Went to the plumbers merchant for a length of 15mm pipe. Man asks how long, I cant remember the metric lengths it comes in, so said 6 foot (needed about half that).

Get a HUGE tirade about going metric and my inability to adapt. Just before he goes into the stockroom he turns and asked ‘Did you say half inch or three quarters’

5. I totally fail to see a problem. When I started High School in 1963, we were informed that all science was going to be done in metric units. That later evolved into SI units. I do a fair amount of carpentry plus some machining work. I hung on to to inches and tenths for a long time, but woke up to the fact that the world had moved on and metricated myself. It took an effort of will.

I don’t have a problem with pints and miles, although the Yanks amuse me with their “half a quart”. Here in fully metric Japan, you buy or rent acommodation by Tatami area. Approx 180×90 cm, or the sleeping area for one (very small) person.

And waffling on. Some of the kit in my wife’s factory had metric fastenings screwed crudely into some machines. Experimentation showed that they weren’t metric or SAE threads (US Imperial) either. A little research showed that Japan (especially the building industry) uses Whitworth fasteners (UK, from about 1850) with metric heads. And also, all of the plumbing is BSP

6. BSP = British Standard Pipe. While we are on pints, make mine a Sam Smiths, thankee very much.

Finally, my Japanese car running on Japanese tyres has 16 inch wheels. Not 40.64cm. Take that Michelin, biff! bash! kersplosh!

7. I bought carpets a few months ago, they were sold in metric.

My preferred solution is to adjust imperial units to match metric: so an inch becomes 2.5cm instead of the awkward 2.54cm, a foot becomes 30cm, a pint becomes a half-litre, one lb becomes a half-kilo, and so on. Yards and stones are obsolete. Lots of blokes become six feet tall overnight, and all women have lost a few lbs.

On second thoughts, perhaps keep the old pint. People complain loudly about beer.

8. I can’t see the problem either. Generally, the things we use Imperial for are rule-of-thumb measures. Describing someone as six foot is adequate for 5′ 11 ¹/²” or 6′ 0 ¹/²” An ounce in cooking doesn’t need to be exactly 28.35g. A mile is where you get to after a quarter an hour’s fast walk. And they’re user friendly measures. Want an ounce, halve a half pound pack, halve & halve again. It doesn’t matter that it’s actually a 250g pack. A third of a foot is 4″ not an infinitely recurring number.
SI measures are for where accuracy is important. 1197mm is a lot easier to handle than Imperial in ¹/³² increments.
The two requirements are different. There’s no real need to convert one to t’other. Heaven knows why they’re trying to teach it.

9. I think I mentioned this when we discussed the subject in the dim and distant past, well before I moved down here and changed names. A golfing friend once told about the trench he was digging at home, it was 10m long x 2′.

I also noticed the the butchery department of the Edeka I was in when visiting the Ahr Valley in October still used the Prussian Pfund alongside grams.

10. It’s interesting that BiJ mentions BSP. BSP threads do a different job to, for instance, metric bolt threads. Bolt threads are cut to put mechanical tension on a connector. BSP threads are cut to provide a seal to a fluid. The thread angles & clearances are suited to the task they perform. You wouldn’t necessarily want them interchangeable..

11. @ dearieme
I do use cubits (to my wife’s irritation) because I always have the measure to arm. Also because it is a useful length.

12. I also like the metric/imperial mix. I rarely find myself confused or confusing other people.

The pint is the ideal unit for serving beer in a temperate climate. But not Sam Smiths.

13. Piss on metric and any who support it.

Imperial to be taught as primary. It won’t hurt kids to learn the French nonsense as well. Keep their brains working.

Time also for the return of £ s d. The extra brainwork will force dumbed down youth to think or be ripped off to shite and back.

The chain-hung corpse of Heath should be hanging at the grand launch. With a mocking parody of that shite-awful “Decimalisation” song by The Scaffold. Though I still like their name.

14. Whenever I visit Canada I am sometimes amused to hear metric and imperial measurements used in the same sentence. I don’t know where else you could buy a board 2 meters long by 4 inches wide. People will give you their height in feet and inches, their weight in kilos, short distances in feet and yards but long distances in kilometers. But yeah, a meter is close enough to a yard for many purposes. Half a kilo is close enough to a pound. A liter is close enough to a quart (or at least to an American quart). Temperatures take some getting used to. It is still hard to think of 30 degrees as hot. If you spend enough time around metric you start to get used it and you may find it’s not hard to adapt.

15. That was my point Bij. I know why metric Japan, and for that matter metric Germany use BSP. I also know why metric Japan uses Whitworth. It’s because Whitworth (the man) was a real engineer, he made a series of test pieces and what became the Whitworth standards had the best strength performance. Metric and SAE are cheap and shit.

In my local hardware store, everything is labeled and colour coded “M” or “W”. The “W” stuff is also labeled 1/4 or 3/8 etc. Also, there are test pieces where you can try your male/female fastenings in order to determine precisely what you have. If our host has a metric/Imperial issue, he’s a dull boy and move to the back of the class.

16. Grow some brain cells if you can’t handle it.

But it is hardly the ‘problem’ it used to be. The interweb will provide instant conversions now, even from furlongs per fortnight. That’s not a joke; it’s there on duh net!

17. The Yanks measure watery things (lakes, rivers, sewers, etc) in acre-feet. Apparently 1 acre-foot is 0.89 Olympic swimming pools. 🙂

18. Further to the above comment relating to Canada, look up “Gimli Glider” for a harrowing account of how a conversion error caused a 767 to run out of fuel mid-flight, forcing it to glide to a safe landing in Gimli, Manitoba.

19. I get to see quite a few engineering drawings in the course of my work, sometimes by enthuisiastic amateurs, sometimes qualified professionals.
Of late, most everyone has moved to creating drawings via CAD programs which has meant nearly everything now is metric and fairly standardised in format. (except those fuckers that use AutoCad and need beating with a clue-stick.)
You do still get the occasional drawing in imperial, especially if the drawings are of american origin. American aerospace is fully metricated, but otherwise old habits die hard.
A personal bugbear are the drawings which mix fractional and decimal imperial dimensions together with metric on the same drawing. Makes reading drawings a pain and dealing with tolerances obnoxious.

20. @Noel Scoper
32mm pipe is 1 1/4″not 1″. And note, pipes are normally measured by their I/D – inside diameter. Their flow capacity being the important number. 1″ plastic is normally electrical conduit but could be overflow pipe. The wall thickness isn’t suitable for constant use.

21. re. the Gimli Glider, it was extremely fortunate that the P1 was also a skilled glider pilot, that knew about deadstick landings, and that he was also a petrolhead, or knew that the Gimli dragstrip was based on an old (but closed) airstrip.
It remains the only instance of anyone (successfully) sideslipping a wide-bodied airliner.

On metric/imperial conversions, wasn’t there a \$bn Mars probe that fell foul of this, and tried litho-braking as a result? (like aero-braking, only slightly to the side, and much more sudden).

IIRC the EU did start to legislate that ONLY metric measures could be used – but gave in when it realised that would close off US/Canada to all exports.

And in pedant mode, how can the base unit of metric mass be the kilogram?

22. bloke in spain
December 16, 2019 at 1:03 pm
It’s interesting that BiJ mentions BSP. BSP threads do a different job to, for instance, metric bolt threads. Bolt threads are cut to put mechanical tension on a connector. BSP threads are cut to provide a seal to a fluid. The thread angles & clearances are suited to the task they perform. You wouldn’t necessarily want them interchangeable..

But then there`s NPT threads which are similar to BSPT but are not interchangeable .
working on CNC machine tools metric is better as they work to 3 decimal places so metric is 0.001 a micron imperial 0.001 a thou ….quite a difference.

23. @BiS:

I did specifiy uPVC pipe (this is water or process industry stuff). The OD of a 1″ uPVC pipe is 1.315″ (33.6mm). The OD of a 32mm uPVC pipe is 32mm.

The rule of diameter is ID does not hold. Different materials and metric/imperial vary dimensions from OD, ID and the average of the two as you go from thin plastic pipe to thick plastic pipe, mild steel, stainless steel, concrete, copper, lined, etc, etc. Then add on various schedules/pipe wall thicknesses for pressure ratings for the “same” diameter where it could be the OD, the ID or both that change with size.

For more confusion, a 1/2″ (now called 15mm) water meter has 3/4″ BSP fittings that require 22mm copper pipe to fit the compression fittings. A 3/4″ meter has 1″ BSP fittings, etc.

Pipes and threads are really fucked up.

24. @ ArthurtheCat – regarding ‘the Yanks’ and acre-feet of water, this unit is normally only used is the context of water-use planning and contracting, as for example in irrigation planning and water-rights issues, and often expressed as part of a quantity of acre-feet per year. In that context, where most of the applications are agricultural, it makes perfect sense – it expresses a quantity of water in a way that is directly-transferable to the units that a farmer would use – acres of land, inches of rainfall, yearly seasons. It’s a fine example of a specific unit perfectly developed to match its specific application.

On the larger issue, almost-all arguments about systems of measure are not actually about measurement at all, but about culture. What is now called the SI system is a system just as irrational and arbitrary as the system now referred to as ‘Imperial’ or ‘customary’ – it’s just that the French decided that what they really needed was their very own irrational and arbitrary system, which they then proceeded to try and impose on everyone else. Arguments about which system is ‘better’ are just asinine – there are as many optimal systems of measure as there are different fields of endeavor, and the idea of trying to impose one constant and identical system on everybody for everything they do is just asinine. It benefits only bureaucrats, which is why it has to be imposed almost everywhere by force of law.

llater,

llamas

25. @Noel Scoper
You are entirely correct. Surprised me. I must have used thousands of feet of it & never actually measured it. I just know what’s 1 1/4, 1 1/2, 2″ etc by looking at it. (And that ghastly gold stuff corner shops used to sell wasn’t compatible with anything else) Probably harking back to iron & lead where you always talked I/D

26. @john77 – WKPD: The cubit is an ancient unit of length that had several definitions according to each of the various different cultures that used the unit. These definitions typically ranged between 444 and 529.2 mm (17.48 and 20.83 in), with an ancient Roman cubit being as long as 120 cm (47 in).

But then the Roman pace was two strides.

27. We might have Napoleon to ‘thank’ for the metric system, but if it wasn’t him, then it would have been someone else to blame. A consistent and integrated measurement system became increasingly necessary with the rise of science, and metrology became a discipline. However it had to be tied at least to the second, since that unit is effectively millennia old and the formally defined value of the unit is based on day length in the middle of the 19th century. Hence the need for leap seconds now as the Earth has slowed down. The metre is arbitrary, though based on the size of the earth, and close enough to former useful units of length. I’m not sure why the kg is the size it is. Anyway, with a lot of effort, they are all now based on defined values of universal constants – c, h, k, N, etc.

28. @Tractor Gent
But Napoleon didn’t like metric. The law of (AFAICR) 1803, he brought in, specifically prevents any Frenchman from being prosecuted for using the old measures. Why France continues to use them today. I’ve bought things in feet & pints in France.
Napoleon was, of course, an artilleryman. And the artillery used its very own system of measures totally incompatible with anything else.

29. 30 years ago when I worked for a large food manufacturer we used to always check to see if stock differences were divisible by 2.2046 as UoM was one of the common entry errors especially as shipping/good in notes was often in metric and the old system was a mix of imperial and metric.

30. Speeds for planes and boats are in knots because that’s essential for navigating with traditional charts as 1 nautical mile is 1/60th of a degree around the great circle. Any other unit would be massively prone to silly errors. All the others look like pretty valid gripes to me though!

31. On a slightly more technical note:

As soon as you start doing anything even quasi-scientific all systems but SI become too unwieldy to use. If you have a current of one amp flowing through a resistance of one ohm it will develop ane volt across it and dissipate one watt of power, which is equivalent to moving the point of application of one newton of force through one metre in one second; if such a force is applied to a mass of one kilogram then it will accelerate at one meter per second squared. If that one amp current flows into an initially uncharged capacitor of one farad capacitance, then the rate of change of voltage across it will be one volt per second, and when there is one volt across it the accumulated charge will be one coulomb. If the rate of change of current through an inductor of one henry is one amp per second, the inductor will develop a voltage across itself of one volt.

Machinists still think in thous rather than microns for surface finish and depth of cut even when they’re working to a metric drawing.

I have noticed astronomers and astrophysicists are still curiously wedded to dynes and ergs, when they really should know better. Cosmologists tend to rescale units so that everything (mass, gravitational constant, speed of light etc.) is one.

32. llamas, the SI system does have the benefit of being internally consistent, but that’s about all.

The ‘threads and bolts’ folk seem to have missed several well-known anecdotes, like the Yanks having to get to grips with UK sizes in order to build Merlins.

I struggled for ages to find new screws for the rear light clusters on my 1970 Lotus, before discovering that the Lucas units used US threads, presumably for export purposes. A nice computer techie at Imperial College extracted exactly the right screws from a worn-out CDC lineprinter for me – but that happened about 40 years ago. You can get whatever you want these days via the internet from China.

33. When I grew up we had an additional Imperial unit, the bottle. An imperial gallon contains 4 quarts and 6 bottles. And an American gallon contains 5 bottles. (Now go and check this out, the US gallon is 5/6 of an ImperiaL gallon) And try multiplying a standard bottle of wine 750cc with 6 and see how accurate you get to official conversion of litres per gallon.

The reason for this is rumoured to be US customs officials in NY who took a bottle out of every box marked one gallon of Whiskey, stating, we are a meric country and we sell in units of 5.

34. Interesting book — “The Measure of All Things”, by Ken Alder — about the French effort to measure the meter (metre for pointy-headed French intellectuals). It was supposed to be a certain fraction of planetary circumference, but (Spoiler Alert!) the French made an arithmetic error. Thus, the meter is as arbitrary as the distance from the king’s nose to his thumb.

A system of units should be fit for purpose. There is no point in measuring the distance to the nearest star in meters, or tire pressure in Pascals. I have always been fascinated by the Imperial gc factor which allowed the normal force of gravity on 1 pound-mass to be an intuitive 1 pound-force — so much more useful than the force of gravity on 1 kilogram (why a thousand grams? Where is the vaunted consistency?) being 9.80665 Newtons. Let’s face it — every measurement system is arbitrary, and has its pluses & minuses.

35. Cosmologists tend to rescale units so that everything (mass, gravitational constant, speed of light etc.) is one.
True, but it makes derived units, e.g. force, rather large. 🙂

Nuclear physicists don’t use pure SI, either – Ångstroms and barns are their thing, and then we get on to “inverse femtobarns” …

36. djc: It’s the pointless precision that irritates. 1600 metres, 1 mile, or 5000 feet would have been perfectly OK for a newspaper report. I’ve even seen this in El Reg items, and complained about it there. We get the same thing converting \$1M into something in £/€ that the ‘thick’ readers can understand. Most people have some sort of intuitive grasp of how big \$1M is from seeing US films, and the exchange rate is so close to 1:1 now that it makes little difference in understanding. Years ago, when you could get over \$2 for a £ and even more for CAD, AUD and NZD then it made more sense to do a conversion.

37. TC, indeed, I wonder where the pointless precisin in the item quoted originated? It looks as if someone started off with a ‘mile’ of some sort and then converted that to feet and metres. Which raises twin doubts about the journalist’s understanding: no intuitive sense of appropriate scale, precision and accuracy, and even more doubt that the original distance was anything like a mile or 1.6km.

[I am quite good at mile/km conversions: familiarity with binary digits breeds familiarity with multiples of 16 combined with two decades of driving LHD imports in GB.]

38. Mixed units don’t bother me.

I’m cooking rice this evening; 250g of rice to 1 pint of water. Works perfectly (cooked with the lid on) – the rice just absorbs the liquid, so no need to drain (which loses nutrients), but it doesn’t dry out and burn on the bottom of the pan.

But it drives my wife mad.

39. Bloke in Japan said:
“A little research showed that Japan (especially the building industry) uses Whitworth fasteners (UK, from about 1850) with metric heads”

I love that.

40. djc said:
“TC, indeed, I wonder where the pointless precision in the item quoted originated?”

It’s usually from having been converted out and back again. Started out as a mile, then converted into km, and then rounded, and then converted back into imperial but not rounded.

41. @ djc
Because the use of “1 mile” is a thoughtcrime.
An example of the difference between precision and accuracy

42. I do like the equivalence that each 10m depth is 1 bar increase in pressure for diving, seem to recall in actuality it’s to a couple of decimal places so not significant enough to matter for most divers

43. The problem with metricification is that the proper old measurements get superseded. This wouldn’t normally be an issue but in some cases is exceptionally important. Here in New Zealand, for example, there is no legal definition of a “pint”. So you order a “pint” in the pub and get a glass of beer containing somewhere between 400ml and 500ml – to get a proper pint you have to go to a British or Irish pub where you get the full 568.26ml of amber perfection. Of course, in the USA, a pint is a much more meagre 473.16ml, which is barely enough to quench your thirst.

It is enough to make one want to come home to Blighty!

44. James in NZ said:
“Of course, in the USA, a pint is a much more meagre 473.16ml”

But that’s probably as much as you’d want of most Yankee beers.

45. @John Wilkinson December 16, 2019 at 2:59 pm

My wife has a 1 litre car

Talking of 1 litre engine, the 2020 Honda Fireblade CBR1000RR-R produces 215bhp

@djc December 16, 2019 at 5:20 pm

BBC does that too and frequently screws up by orders of magnitude

I heard newsreader on R4 say 26cm of rain fell in TownX in one hour

46. @ Bloke in Costa Rica :

“As soon as you start doing anything even quasi-scientific all systems including SI become unwieldy to use.”

There, FIFY.

The train of consistency you describe, while absolutely accurate, does not represent anything quasi-scientific outside of a textbook example. The real world is filled with adjustments, corrections and factors which affect every system of measure, and adds a similar unwieldiness to all of them.

Many ‘customary’ or ‘imperial’ units of measure actually have very-similar consistency within a range of parameters to be measured. I take as my example the surveyor’s chain, Gunter’s chain. This is a very old measuring tool used for measuring land. It’s often derided by the metrically-addicted, purely on the basis that a) it’s very old and b) they don’t actually know what it is or how it works. Har, har, har, measuring with a chain, how bizarre!

But in fact, Gunter’s chain was devised by something of a mathematical genius, Edmund Gunter, who managed to create a measuring device that would measure both length and area in both traditional (base 2) and decimal (base 10) math. It has superior consistency in measuring length and area as the SI system, and predates it by some 150 years. Which is probably why it is still the basis unit of land measurement across the majority of the US – virtually the entire Louisiana Purchase was measured this way, because it worked, and it works to this day. Why change?

Ralph Waldo Emerson wrote that ‘A foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines’ and nowhere is this more true than in the pedantic insistence by some that we should all use one and only one system of measure for absolutely everything that anyone ever does anywhere – purely for the sake of ‘consistency’.

llater,

llamas

47. @RichardT That’s exactly how I cook rice. With the same result. However she-who-insits-on-cooking uses about 4 times as much water, boils it furiously & ends up with it charred to the bottom of the pan. Yet she’s from a culture that eats a lot of rice whereas I’d rarely eat it, if I was on my own. Don’t even particularly like the stuff. If I’d wanted to be a third world peasant I’d have chosen my parents more carefully.

48. @excavator man: “the SI system does have the benefit of being internally consistent, but that’s about all.”

Not quite. The unit of molarity is based on the gram rather than the kilogram. And that is not the only example of the perversity of chemists. They insist on still using the litre, though they incline to disguise it sometimes as dm^3. Come to think of it, though, they still use the ml, so conserving the litre by the back door.

49. BiS, my missus cooks rice the same way yours does; but mine is English, so one wouldn’t expect her to be able to cook foreign food. I only cook the stuff because I haven’t persuaded her of the joy of curry on chips.

50. The rule for rice is, in whatever units you want, one volume of rice, two volumes of water; heat until boiling; be sure lid is on, reduce heat to minimal possible simmer, wait exactly 20 minutes and serve. As noted above, all water absorbed, nothing burned, and easy to remember and scale.

Use glass lids; then you can see you’ve done it right.

51. @ BiND
It doesn’t really matter what system of measurement is used as long as everyone understands the system that he/she/they are using. FTFY

I grew up with the Imperial system which employs is practically useful units but requirres elementary mental arithmetic (except in chemistry and some physics lessons which used metric), my sons were taught metric (which does not require any arithmetical ability but has inconvenient units which is why the livre continued in use in France until WWII, probably later) so I periodically have to remember to divide by 39.37 or 2.2 or multiply by 1.6: not a major problem.

52. @john77
Livres and pfunde are in still common usage in French and German markets (at the very least, they’ll understand what you’re asking for), though you’ll probably get a 500g portion. All French ads for TVs show the screen size in pouces (inches).

53. Ah aviation!!

The reason that fuel is measured in Kgs or Lbs is because volume changes with air pressure and temperature.

You might have added the altitude can be passed in millibars/inches and that the transition altitude is a variable, and don’t mention QNH, QFE and regional pressures, depending on the country. Headings also being passed in magnetic for airfields and in true for airways etc, and let’s not talk about variation.

Then of course there are the maps, OS, MGRS or Lat and Long? And is that degrees, minutes and seconds; degrees and decimal minutes or decimal degrees? Then, of course, are they locally produced maps in the local geodetic datum or WGS84, and do you know how to change the settings in your navigation system?

Thank god cloud is passed in good old fashioned oktas…….

54. And when in Italy you buy things at the market by the ETTO which is 100g but I believe is actually a hangover of a much older unit that just happens to approximate to 100g.

My own view is that if you’re using a unit that has to be raised to several powers of ten to measure something useful in real life (or conversely divided into some insane milli- or micro- fraction) then it was the wrong unit to start with. Hecto-pascals anyone? Ffs.