Obviously there are a variety of languages spoken around the world, but the world has also developed many other localisations that serve as barriers.
All create challenges to discussion being able to be understood across the globe.
Plus they create difficulties in using products designed in one location, being used elsewhere, and the surprising thing is, despite all the standards bodies, it just keeps happening.
This page is built as reference to the different systems, and what is in use where, in an effort to enable interpreting data not expressed in familiar terms.
Measurement: SI Units vs Imperial and Others.
SI ‘System International Units and Metric units.
There is a global standard system of measurement: The International System of units or System Internationale (SI).
The SI system with 7 core units of measure, supersedes the older metric system that has only 3 units because no measure for electricity, temperature, the amount of light, and amount of a substance (moles) were included in the original metric system.
The Metric system replaces what are usually the most cumbersome traditional measurements with a simpler, clear and internationally agreed specification. SI goes further, adding core units to provide an international standard for measuring anything that can be measured.
Everything worldwide, not just the units of SI, is based on the the SI standards. Even the feet, inches, pounds etc in the USA are in fact defined by converting from a specific number of metres and, grams etc.
Beyond the base 7 Units: 22 derived units, and 14 ‘accepted’ Non-Si Units.
Derived Units: The Combinations, reciprocals and Celsius.
There are 7 units because there are seven recognised independent things to measure. Then there are 22 other units which all are based on one or more of those core 7 units. Litres does not even make the ‘derived’ units, but Celsius as a unit of temperature, although all other derived units, as listed here, are names for a combination of the base units raised to some exponent.
Non-SI, but ‘Accepted’ Units (Oh, if you must!): Litres, Hectares, Metric Ton, Hour, Minutes, Days etc.
Somewhat surprisingly, litres are not an SI unit. At 10cm cubed, or 0.1 metres cubed, they are on m(m3) or 1/1,000th of a cubic metre. In some ways if would have been better if the named unit was metre cubed, but the conversion is simple. The 1cm cubed becomes 1,000,000th of a cubic metre and 1,000th of a litre and is know as the
All but 3 countries officially adhere to use of SI (‘metric’) units.
It sometimes seems like USA vs the world on this one, but there are two other countries, Myanmar and Liberia, that have not officially committed to the SI and metric system. Despite all the commitments, very few people stick to SI units all the time. in practice, a mixture of metric and imperial is in use in most countries, with Myanmar being alone in sticking with their own system.
Non-SI, Non-Acceptable Units: Length, Weight, Temperature, Horsepower, Torque.
So what units are in use outside the acceptable ones?
- USA uses Imperial Weights: grain, dram, ounce, pound, stone, quarter, hundredweight, ton.
- Liberia, uses the same system, and as noted below, some other countries use some measures from this system particularly Canada and to some extent the UK sometimes use weight in pounds.
- Myanmar Weight: 12 units of there own I cannot even pronounce listed here, but in practice mostly SI.
- USA uses Imperial Weights: grain, dram, ounce, pound, stone, quarter, hundredweight, ton.
- USA uses imperial lengths with include: inch, foot, yard, rod, furlong, mile and league.
- This syste
- Myanmar Lengths: 13 units I cannot even pronounce listed here, but in practice, mostly use of SI Units.
- Liberian Lengths: Mostly SI units, but yards are still also used and there is no rule so you could use whatever you wish.
- Others: UK and other countries still sometimes use imperial units of length, which are the same as those used in the US.
- USA uses imperial lengths with include: inch, foot, yard, rod, furlong, mile and league.
- USA uses a unique system: Weight: grain, dram, ounce, pound, stone, quarter, hundredweight, ton.
- Myanmar Weight: 12 units I cannot even pronounce by listed here.
- Liberian Weights: Mostly SI units, for weight, but there is no rule so you could use whatever you wish
- The US and Liberia use Fahrenheit for temperature, as do 5 small countries who officially use SI units.
Units in the USA In practice.
Non SI units for length, weight and temperature persevere in the USA. In fact while at one time car speedometers all also had km/h in addition to miles/h, now common use has reverted to miles only. In science, all units are standard, and many industries use of standard units to facilitate international exchange, which for a percentage of Americans leaves them the main people of the world who must deal with not just a more complex system, but both two systems.
Non-SI Units are still in use beyond the 3 Non-SI countries.
Screen Size is often in inches in fully metric countries: worldwide.
Display size: A diagonal measure in inches are common worldwide. Take an international web site such as gsmarena.com which focuses on mobile devices. Reading specifications for the Samsung Fold3 or the iPhone 12 give dimensions of a phone as millimetres, and sometimes also provide inches in brackets afterwards, but the headline number for screen size is the diagonal in inches, followed by the area in cm2.
Height of people and mountains can be in feet in metric countries: On occasions in many countries.
Some people in some countries still describe a persons height in feet an inches, even in countries using metric units for almost everything else. Younger people may use metric and older people feet and inches, but national news can still use feet and inches. Elevation of an aircraft is also sometimes given in feet even in countries using metric, especially the UK, where depth of water and also be given in feet.
Temperature: 7 countries still use Fahrenheit.
United States, Bahamas, Cayman Islands, Liberia, Palau, The Federated States of Micronesia and the Marshall Islands are listed as using Fahrenheit and a few other countries use both systems, but the population outside the US who understand Fahrenheit is very small.
Distance: Miles still used the ‘metric’ UK .
The British still use miles to measure distances by road. also have not committed to use of metric units either. use ‘imperial’ measurements, although neither use US gallons. The US did officially become metric
Gallons, Quarts, Pints and Cups for Volume in the UK.
Traditionally large amounts of volume were measured in gallons, and smaller amounts in cups.
In theory, 16 cups, 8 pints, or 4 quarts make one gallon, which makes sense, but in practice, as there are three ‘gallons’:
- US fluid gallon
- US dry gallon
- Imperial gallon
Taking a ‘cup’ from a recipe could mean one of five different fractions of a gallon depending on where the recipe was written in which gallon. Still, the UK today uses the imperial gallon, and the US uses the US gallon. The English also had lots of different ‘gallons’ for different things until 1824, when they standardised all gallons to be around the size of what was at the time the ‘beer gallon’, despite the ‘wine gallon’ being in wider use at the time. The US always used that more common ‘wine gallon’ which is the basis of the US gallon.
Generally, a mess. But at 3 different gallons sizes remain in use. In the UK they buy fuel in litres, but still measure fuel economy in miles per gallon (imperial gallons) and buy beer in pints (imperial pints) and have recipes using cups(1 imperial cup= 1.2 US cups).
Speed Limits In Miles per hour in the UK and 13 other countries.
There is a full list here, but apparently around 9% of the world population uses mph, with almost all in the US and UK, but Belize, and some Caribbean nations and US and UK territories and protectorates.
Fuel Consumption / Economy: ‘mpg’ vs l/100km.
It is logical that all countries who use mph speed limits, as above, also use ‘mpg’ for fuel economy. As discussed below, there is no universal rule for what unit to use for fuel consumption/economy.
Power: Horsepower is used in many metric countries.
Horse Power still used in place of kilowatts: UK, France, Canada in addition to USA. In place like Germany, Sweden, Hungary etc, horsepower is in common usage as well as kilowatts. In other countries such as Australia, the term is sometimes horsepower, but the only unit is use is kilowatts, as in “What horsepower does your car have, is it more than 200 kilowatts?”.
As even the USA measures electrical power in the metric unit of kilowatts, it will be interesting to see what happens as electric cars become more common.
Time: The Global, but Messy Measurement?
Travel, Communication, and The Need to Agree On One Global Time System.
Most societies currently measure ‘time’ as a combination of date and time. Every society has the same concept of day, and the same concept of ‘year’ and generally developed a way of dividing a day into different periods of time. Every watch or clock records hours, minutes and seconds, and even countries with different new year celebrations and alternative calendars, also recognise and mainly work with the same system of months and years.
Today, worldwide there is an agreed system of keeping time, calendar, even where societies have their own additional year numbers and festivals for the start of a year. There is only one system for measuring time within a day, with clocks and watches the same the world over.
Overview: How did we get here.
History: How travel and communications gave use a universal system.
At one time locations could use a sundial to determine time of day. Midday was when the Sun was at its peak. This meant at midday in London, it was not yet midday Bristol which is around 160km to the west and the Sun cannot be directly overhead in both places at the same time. This was ok when people had to walk or travel by horse and carriage, but as travel improved the idea that a watch had to be reset by a few minutes at every town on an east-west railway line became unworkable. Then there was the telephone, with everyone in within a country able to speak to each other, the need to have a common understanding of time became essential.
Date keeping started long before people needed precise times.
Natural Time Intervals and Arbitrary Time.
The Day: Natural, but more than one rotation of the Earth.
All units of time from nature are imprecise, and the primary natural unit of time is the day.
The day becomes rather obvious to any living creature, and while the length of the day is almost constant, it does change throughout the year. While the Earth rotates at a constant speed, it takes approximately 23hours and 56 minutes for one rotation, and then approximately 4 minutes to rotate the little extra required to adjust for Earth having moved in its orbit in that day, and face the sun in its new position. Each day means 1/365th of the journey around the sun, so 1 day further through the orbit around the Sun is just over 1 degree in position, and so without extra rotation, all the stars would be back in the same position, but the Sun would have moved. For the same time of day we want the sun in the same position, not the stars in the background, so we include the extra four minutes of rotation to keep the Sun in a fixed position, and think of the stars, which are in fact fixed, as moving in the sky throughout the year.
However it is not quite a fixed four minutes. As the orbit of the Earth is not quite circular, but slightly elliptical, the distance from the Sun varies throughout the year with the closest (perihelion) point in early January and the furthest (aphelion) point occurring in July. As this also results in the Earth moving fastest when closest to the Sun and slowest when furthest, it also means that approximately 4 minutes to adjust for the Sun being repositioned in the sky takes a little longer in January than in July! This is compounded by the tilt of the Earth, and in summary, the length from noon-to-noon can vary by over 45 seconds throughout the year.
Not enough for the casual observer to notice the sun being out of position due to clocks using a fixed length day, but enough to illustrate that the day is not a perfect fixed length period of time.
Given the length of days actually varies from the theoretical 24hrs or 86,400 seconds, it is not surprising that no only are days not exactly 86,400 seconds individually, but even on average they vary slightly from theory, thus requiring leap seconds to be added around once every 21 months to keep midday close to noon at the centre of time-zones.
The fact that we need leap seconds, means a perfectly accurate mechanical chronometer, would still not keep perfect time without adjustment.
The Month: Natural, based on the Moon, but not in sync with the moon.
Months originally must of corresponded with the cycle of the moon, and while they are sort of close, with lengths of every month but February set at 30 to 31 days, when a true lunar month is approximately 29.5 days. But not only is there not an exact number of days in a lunar month, there is not an exact number of lunar months in a year. In reality calendar months other than February are between 0.5 and 1.5 days longer than lunar months.
At one time the calendar started with March and ran through ten months until December, leaving the end of the year in winter not being part of any month. January and February were originally created to absorb the extra days are the end of the year, with the Roman calendar starting at 1st March until 154BCE. As the last month added, February was burdened with changing in length to correct for the length of the year.
The Year: Natural, and again, neither an exact number nor constant.
The year is also natural but is neither an exact number of days (approx 365.242) or rotations of the Earth (close to 366.2242) Not only is the number not an integer multiple of days, it also changes. Which is why the calendar needs to keep adjusting.
If the ancient scholars new the precise number of days in a year, instead of estimating at 360 days, a circle might no have 360 degrees, but either 365.25 degrees, or they would have realised it is all too hard. The sun each day moves almost 1 degree of it orbit around the sun, but not quite.
There have been many failed attempts to rationalise time.
Most start with trying to divide a day or some other natural unit of time into small fractions, just as the current system divides a day into 86,400 seconds. As an example, you could start with a day, and divide into 100,000 ‘new seconds’.
The problems is, even the average length of a day will change over time, so either the length of a ‘new second’ must also be flexible, or more practically, just as we need leap seconds to keep days aligned now, we would still need ‘leap new-seconds’, so 1,000 days would not be exactly 1,000 x 100,000 ‘new seconds’. The main benefits of of having an a convenient number of ‘new seconds’ in a day, would break down over longer times.
An alternative would be to leave the second at the current length, and have longer times of 1,000 seconds. Lets call there kilo-seconds as ‘quours’ for short, as at 16 2/3 minutes, each ‘quour’ would be just over the current ‘quarter-hour’. Most times of day could be represented quite usefully in this new system, but adjustments of a few minutes or ‘deci-quour’s, to keep number as simple as possible. ‘9 till 5’ would best become 32 to 60, unless we wanted to work 30 extra of todays minutes and make it 30 to 60.
The challenge to gain never having to convert between second, minutes and hours anymore, would not be the new numbers for times so much as the fact that an analogue clock would no longer have hands automatically in the right position to start a new day. Digital clocks would be easy, but analogue clocks would be more difficult.
Electrical Energy: kwh or Joules?
The kilowatt hour is used internationally to measure electricity consumption. However, electricity consumption is energy, and there is a standard unit of energy, the joule. You might think that, since with the metric system everything is in multiples of 10, there should be a direct conversion that is some multiple of 10, but unfortunately, no, as there is no metric time, and joules are based on seconds, not hours.
1 Watt second = 1 joule
seconds in an hour = 60 x 60 = 3,600 1 Watt hour = 3,600 watt seconds = 3,600 joules = 3.6 kilojoules (3.6 kJ) 1kW hour = 1,000 x 3,600 watt seconds = 3,600,000 joules = 3.6 megajoules (3.6 MJ)
To be fully metric would be to use MJ in place of kwh, thinking of an hour in terms of the number of seconds is not something to which people are accustom.
Energy Consumption / Economy: mpg, l/100km, m/kWh, mpg-e, kWh/100km, wW/km.
Consumption is a better measure than Economy!
Two types of measure are used:
- fuel economy: the higher number is better
- fuel consumption: the lower number is better
These are two different perspectives on the same specification. Economy is the inverse of consumption, and as the video here points out, it is much easier to do calculations using consumption than economy. The reason consumption can be used in calculations is that it is the direct measurement of what the car does:
- the car can travel at a measured speed
- for a given speed the car consumes fuel at measured rate
The rate of consuming fuel is a single measurement, while distance travelled per amount of fuel used is an indirect measurement from combining the data.
Most often as countries moved away from imperial measurement, they moved to l/100km to measure fuel consumption. But what to use for electric cars has not quite stabilised yet.
Despite it being much better work with consumption than economy, most countries started with economy, and then switched when they changed units. In part because countries mostly started with miles and gallons, and because the nature of the units, ‘miles per gallon’ gives a convenient number, while ‘gallons’ are just too large for ‘gallons per mile’ to give a convenient number and working with “fluid ounces per mile” would be worse as no one wants to measure fuel in fluid ounces.
MPG(mpg): Miles per gallon, impractical, but a clear easy number.
Miles per gallon, a measure of economy, was the main measure at one time in most English speaking countries, and remains the main measurement in the US and UK today (although a different number in each country as gallons differ). While measuring economy, as again pointed out in the video, is sort of measuring reduction in consumption, is impractical, and makes calculations complex and error prone, MPG results in very convenient numbers. Gallons per mile would be small fraction, and even gallons per hundred miles would result in numbers like 3, 4, 5 which would mean one or two decimal place would need for useful comparisons. The solution would be to use a smaller measure than gallons, but in the imperial system, conversions between the smaller measures itself is complex, or resort to per thousand miles, but picturing a thousand miles becomes more abstract and less relevant most of the time.
For an imperial measurement, despite the problem of miles per gallon being an inverse measure, it is the most practical available.
MPGe and mi/kwh: MPG equivalent and Miles per kilowatt hour.
Since electric cars use kilowatt hours of electricity (kWh) and not gallons of liquid, it may seem logical to not longer use gallons, but in the USA, MPGe or “miles per gallon equivalent” is sometimes used as a measure of electric vehicle efficiency. Yes, this is staying with efficiency rather than consumption.
For the purpose of comparison, one gallon of hypothetical fuel is considered to be 33.7kWh of energy.
This means the MPGe must be divided by 33.7 to give “miles per kWh”, so a vehicle rated at 150 MPGe would travel 150 ÷ 33.7 = 4.45 miles per kWh. This reveals the problem with miles per kWh, the number is small and thus requires decimal places to have sufficient precision.
Using imperial units for consumption could be kWh per mile, but are more typically kWh per 100 miles, because the the kWh per mile numbers are too small.
kWh/100km and Wh/km.
While km/kWh is occasionally used as a the measure of efficiency, most locations that have moved to metric, have also moved to the easier to work with practice of measuring consumption, which makes kWh/100km and Wh/km the common readings. Some people prefer kWh/100km, as it is most similar to litres per 100km typically used for fossil fuel vehicles, and kWh (kilowatt hours) are used more often than Wh (Watt hours), while others prefer Wh/km because it is less complex. Wh/km does require people to realise it takes 1 kW is 1,000 Watts but no only is it shorter to write, many people find thinking of thinking of how many Watts to travel 1 km more relatable.
Convert the units in the left column to the units of the column with heading of the desired units.
|to get ->||MPGe||mi/kWh||kWh/100mi||kWh/100km||Wh/km|
|MPGe||MPGe÷33.7||3,370 ÷ MPGe||2,094 ÷ MPGe||20,940 ÷ MPGe|
|mi/kWh||mi/kWh x 33.7||100 ÷ mi/kWh||62.13 ÷ mi/kWh||621.33 ÷ mi/kWh|
|kWh/100mi||3,370 ÷ MPGe||100 ÷ kWh/100mi||kWh/100mi ÷ 1.6||kWh/100mi÷0.16|
|kWh/100km||2,094 ÷ kWh/100km||62.13 ÷ kWh/100km||kWh/100km x 1.6||kWh/100km ÷ 10|
|Wh/km||20,940 ÷ Wh/km||621.33 ÷ Wh/km||kWh/100mi x 0.16|
kWh/100km x 10
Giz Explains: Why Every Country Has a Different F#$%ing Plug
There is actually a proposed international standard, and it does accept the most commonly used plug in the world.
The challenge is to get people to move from an already entrenched system to another system.
- 110v: (100v-127v):
- North America, Japan & Taiwan
- USA, Canada, Japan, Mexico, Taiwan
- Central America (Except Belize)
- Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, Panama
- The Top of South America
- Columbia, Ecuador, Venezuela
- Most of the Caribbean.
- Bonaire, Cayman Islands, Curacao, Dominican Republic, El Salvador, Haiti, Jamaica, Puerto Rico, Saba, Turks and Caicos Islands, Trinidad & Tobago
- US Influenced Locations in the Pacific
- Marshall Islands, Palau, Virgin Islands(US and British),
- North America, Japan & Taiwan
- Both 100v and 230v:
- Brazil, Cuba, Guyana, Belize, Saint Vincent and the Grenadines, Sint Eustatius, Suriname.
- 230v: (220v-240v)
- Anywhere not listed above.
- Europe, Asia (excluding Japan & Taiwan), Australasia, Most of South America, Most of Africa.
- Dominica, Grenada, Monserrat
Electric Vehicle Charging.
See dedicated page.
DC Home Power: USB?
A standard fro DC power at home is needed, and this sections is to be added.
NTSC, Secam, PAL, 4k, HD
…the history and to be added…
Phone & Mobile Phone Systems.
Every country had a phone system using numbers, but the way to dial a number differed. In the US, a ‘1’ prefix means ‘from another area’, while in most countries a ‘0’ is used. Dialling internationally has different rules from country to country, although mobiles are bringing in some global standards and now internationally it is generally agreed that a ‘+’ indicates an international number. work in progress … more to be added…
At first, mobile phone systems could even vary within the one country, but with ‘global system for mobiles’, eventually it became possible to use a single mobile device while travelling the world. This still works today, but as countries move to a wide variety of differing 5G frequencies, this ability to roam could be under threat.
work in progress … more to be added…
- 2021 May 20: Moved EV charging to a dedicated page.