Why would we want the metric system?

Let's face it: The metric system is the better system!

Why better?

Because it's so much simpler and easier to use.

The metric system is an improvement over the English system in three major points:

1. One unit of measurement for each physical quantity. No matter from which other quantities of the SI system derived, yields always the same unit.
2. Scalability by prefixes - combinations of prefix and unit make for a plethora of convenient combined units.
3. Decimal system - fractions are expressed in decimal notation. Not only makes this the notation unique, exhaustive and intuitively comparable, but also allows unit conversion without doing math - simply by shifts of the decimal point.

Why is this better?

Let's compare the metric system with the English system in these three points to show why the metric system is better:

1. One unit of measurement for each physical quantity

   To compare both systems here, we will list all English Imperial units in use, and all SI units describing the same range of the same physical quantities. These are: Length, area, volume, mass, force, pressure, energy, power and temperature. For a fair comparison, we omit those SI units which are commonly used in both systems, like second, ampere, volt, ohm etc.

   To measure the above mentioned quantities in the English Imperial system, all the following units can occur:

   1. Length: inch, foot, yard, mile, fathom, rod, furlong, league, mil, pole, perch, hand, link, chain
   2. Area: square inch, square foot, square yard, acre, square mile, township, square fathom, square rod, square furlong, square league, square mil, square pole, square perch, square hand, square link, square chain
   3. Volume: gallon, liquid quart, dry quart, liquid pint, dry pint, fluid ounce, teaspoon, tablespoon, minim, fluid dram, gill, peck, bushel, cubic inch, cubic foot, cubic yard, cubic fathom, cubic rod, cubic furlong, cubic mile, cubic league, cubic mil, cubic pole, cubic perch, cubic hand, cubic link, cubic chain
   4. Mass: pound, apoth. pound, ounce, apoth. ounce, dram, apoth. dram, grain, spoth. scruple, pennyweight, short hundredweight, long hundredweight, short ton, long ton
   5. Force: pound, ton
   6. Pressure: pounds per square inch, pounds per square foot, pounds per square yard, pounds per acre, pounds per square mile, pounds per township, pounds per square fathom, pounds per square rod, pounds per square furlong, pounds per square league, pounds per square mil, pounds per square pole, pounds per square perch, pounds per square hand, pounds per square link, pounds per square chain, tons per square inch, tons per square foot, tons per square yard, tons per acre, tons per square mile, tons per township, tons per square fathom, tons per square rod, tons per square furlong, tons per square league, tons per square mil, tons per square pole, tons per square perch, tons per square hand, tons per square link, tons per square chain
   7. Energy: calorie, inch-pound, foot-pound, yard-pound, mile-pound, fathom-pound, rod-pound, furlong-pound, league-pound, mil-pound, pole-pound, perch-pound, hand-pound, link-pound, chain-pound, inch-ton, foot-ton, yard-ton, mile-ton, fathom-ton, rod-ton, furlong-ton, league-ton, mil-ton, pole-ton, perch-ton, hand-ton, link-ton, chain-ton
   8. Power: horsepower, inch-pound per second, foot-pound per second, yard-pound per second, mile-pound per second, fathom-pound per second, rod-pound per second, furlong-pound per second, league-pound per second, mil-pound per second, pole-pound per second, perch-pound per second, hand-pound per second, link-pound per second, chain-pound per second, inch-ton per second, foot-ton per second, yard-ton per second, mile-ton per second, fathom-ton per second, rod-ton per second, furlong-ton per second, league-ton per second, mil-ton per second, pole-ton per second, perch-ton per second, hand-ton per second, link-ton per second, chain-ton per second
   9. Temperature: degrees Fahrenheit

   To measure the same range of the same quantities in the metric system, only the following units can occur:

   1. Length: meter
   2. Area: square meter (are)
   3. Volume: cubic meter (liter)
   4. Mass: gram (metric ton)
   5. Force: newton
   6. Pressure: pascal
   7. Energy: joule
   8. Power: watt
   9. Temperature: kelvin (degrees Celsius)

   combined with none or one of the following prefixes:

   micro, milli, centi, deci, deca, hecto, kilo, mega

   Now judge for yourself which units are easier to keep in your head — the mess of the English system, or the simple metric units!

2. Scalability by prefixes

   Human beings can handle small whole numbers (0 to 999) better than huge numbers (e.g. 190080000), decimals (e.g. 0.672) or fractions (e.g. 77/256). That's why you want units that are close to the size of the thing you are measuring, so the resulting value is most likely to be a small whole number.

   The English system addresses this problem by specifying all kinds of distinctly named, arbitrarily sized units. This causes two problems:

   First, due to the unsystematic definition of the units, conversion between units is nearly impossible, as

   • you have to remember all the unit names
   • remember the chaotic plethora of conversion factors between them
   • worst of all - multiply and divide by them!

   And please don't say you don't have to convert between units because you do have to!

   Have a look at the following three tables showing all the weird conversion factors you would need to know to convert between not even all, but only the most common English Imperial units of the most important three quantities — length, volume and mass. Bold face numbers are key factors. Here goes a glance of the insanity of the English Imperial system:

   LENGTH	mils	inches	links	feet	yards	fathoms	rods	chains	furlongs	miles	leagues
   mil	1	1/1000	1/7920	1/12000	1/36000	1/72000	1/198000	1/792000	1/7920000	1/63360000	1/190080000
   inch	1000	1	25/198	1/12	1/36	1/72	1/198	1/792	1/7920	1/63360	1/190080
   link	7920	7 23/25	1	33/50	11/50	11/100	1/25	1/100	1/1000	1/8000	1/24000
   foot	12000	12	1 17/33	1	1/3	1/6	2/33	1/66	1/660	1/5280	1/15840
   yard	36000	36	4 6/11	3	1	1/2	2/11	1/22	1/220	1/1760	1/5280
   fathom	72000	72	9 1/11	6	2	1	4/11	1/11	1/110	1/880	1/2640
   rod	198000	198	25	16 1/2	5 1/2	2 3/4	1	1/4	1/40	1/320	1/960
   chain	792000	792	100	66	22	11	4	1	1/10	1/80	1/240
   furlong	7920000	7920	1000	660	220	110	40	10	1	1/8	1/24
   mile	63360000	63360	8000	5280	1760	880	320	80	8	1	1/3
   league	190080000	190080	24000	15840	5280	2640	960	240	24	3	1

   VOLUME

   minims

   fluid drams

   teaspoons

   tablespoons

   cubic inches

   fluid ounces

   gills

   cups

   liquid pints

   dry pints

   liquid quarts

   dry quart

   gallons

   pecks

   cubic feet

   bushels

   cubic yards

   minim

   1

   1/60

   1/80

   1/240

   77/20480

   1/480

   1/1920

   1/3840

   1/7680

   385/3440672

   1/15360

   385/6881344

   1/61440

   385/55050752

   77/35389440

   385/220203008

   77/955514880

   fluid dram

   60

   1

   3/4

   1/4

   231/1024

   1/8

   1/32

   1/64

   1/128

   5775/860168

   1/256

   5775/1720336

   1/1024

   5775/13762688

   77/589824

   5775/55050752

   77/15925248

   teaspoon

   80

   1 1/3

   1

   1/3

   77/256

   1/6

   1/24

   1/48

   1/96

   1925/215042

   1/192

   1925/430084

   1/768

   1925/3440672

   77/442368

   1925/13762688

   77/11943936

   tablespoon

   240

   4

   3

   1

   231/256

   1/2

   1/8

   1/16

   1/32

   5775/215042

   1/64

   5775/430084

   1/256

   5775/3440672

   77/147456

   5775/13762688

   77/3981312

   cubic inch

   265 75/77

   4 100/231

   3 25/77

   1 25/231

   1

   128/231

   32/231

   16/231

   8/231

   3200/107521

   4/231

   1600/107521

   1/231

   200/107521

   1/1728

   50/107521

   1/46656

   fluid ounce

   480

   8

   6

   2

   1 103/128

   1

   1/4

   1/8

   1/16

   5775/107521

   1/32

   5775/215042

   1/128

   5775/1720336

   77/73728

   5775/6881344

   77/1990656

   gill

   1920

   32

   24

   8

   7 7/32

   4

   1

   1/2

   1/4

   23100/107521

   1/8

   11550/107521

   1/32

   5775/430084

   77/18432

   5775/1720336

   77/497664

   cup

   3840

   64

   48

   16

   14 7/16

   8

   2

   1

   1/2

   46200/107521

   1/4

   23100/107521

   1/16

   5775/215042

   77/9216

   5775/860168

   77/248832

   liquid pint

   7680

   128

   96

   32

   28 7/8

   16

   4

   2

   1

   92400/107521

   1/2

   46200/107521

   1/8

   5775/107521

   77/4608

   5775/430084

   77/124416

   dry pint

   8936 312/385

   148 5468/5775

   111 1367/1925

   37 1367/5775

   33 1921/3200

   18 3571/5775

   4 15121/23100

   2 15121/46200

   1 15121/92400

   1

   107521/184800

   1/2

   107521/739200

   1/16

   107521/5529600

   1/64

   107521/149299200

   liquid quart

   15360

   256

   192

   64

   57 3/4

   32

   8

   4

   2

   1 77279/107521

   1

   92400/107521

   1/4

   11550/107521

   77/2304

   5775/215042

   77/62208

   dry quart

   17873 239/385

   297 5161/5775

   223 809/1925

   74 2734/5775

   67 321/1600

   37 1367/5775

   9 3571/11550

   4 15121/23100

   2 15121/46200

   2

   1 15121/92400

   1

   107521/369600

   1/8

   107521/2764800

   1/32

   107521/74649600

   gallon

   61440

   1024

   768

   256

   231

   128

   32

   16

   8

   6 94074/107521

   4

   3 47037/107521

   1

   46200/107521

   77/576

   11550/107521

   77/15552

   peck

   142988 372/385

   2383 863/5775

   1787 697/1925

   595 4547/5775

   537 121/200

   297 5161/5775

   74 2734/5775

   37 1367/5775

   18 3571/5775

   16

   9 3571/11550

   8

   2 15121/46200

   1

   107521/345600

   1/4

   107521/9331200

   cubic foot

   459603 9/77

   7660 4/77

   5745 3/77

   1915 1/77

   1728

   957 39/77

   239 29/77

   119 53/77

   59 65/77

   51 46029/107521

   29 71/77

   25 76775/107521

   7 37/77

   3 23037/107521

   1

   86400/107521

   1/27

   bushel

   571955 333/385

   9532 3452/5775

   7149 863/1925

   2383 863/5775

   2150 21/50

   1191 3319/5775

   297 5161/5775

   148 5468/5775

   74 2734/5775

   64

   37 1367/5775

   32

   9 3571/11550

   4

   1 21121/86400

   1

   107521/2332800

   cubic yard

   12409284 12/77

   206821 31/77

   155116 4/77

   51705 27/77

   46656

   25852 52/77

   6463 13/77

   3231 45/77

   1615 61/77

   1388 60052/107521

   807 69/77

   694 30026/107521

   201 75/77

   86 84394/107521

   27

   21 74859/107521

   1

   MASS

   grains

   apoth scruples

   pennyweights

   drams

   apoth drams

   ounces

   apoth ounces

   apoth pound

   pounds

   short hundredweights

   long hundredweights

   short tons

   long tons

   grain

   1

   1/20

   1/24

   32/875

   1/60

   2/875

   1/480

   1/5760

   1/7000

   1/700000

   1/784000

   1/14000000

   1/15680000

   apoth scruple

   20

   1

   5/6

   128/175

   1/3

   8/175

   1/24

   1/288

   1/350

   1/35000

   1/39200

   1/700000

   1/784000

   pennyweight

   24

   1 1/5

   1

   768/875

   2/5

   48/875

   1/20

   1/240

   3/875

   3/87500

   3/98000

   3/1750000

   3/1960000

   dram

   27 11/32

   1 47/128

   1 107/768

   1

   175/384

   1/16

   175/3072

   175/36864

   1/256

   1/25600

   1/28672

   1/512000

   1/573440

   apoth dram

   60

   3

   2 1/2

   2 34/175

   1

   24/175

   1/8

   1/96

   3/350

   3/35000

   3/39200

   3/700000

   3/784000

   ounce

   437 1/2

   21 7/8

   18 11/48

   16

   7 7/24

   1

   175/192

   175/2304

   1/16

   1/1600

   1/1792

   1/32000

   1/35840

   apoth ounce

   480

   24

   20

   17 97/175

   8

   1 17/175

   1

   1/12

   12/175

   3/4375

   3/4900

   3/87500

   3/98000

   apoth pound

   5760

   288

   240

   210 114/175

   96

   13 29/175

   12

   1

   144/175

   36/4375

   9/1225

   9/21875

   9/24500

   pound

   7000

   350

   291 2/3

   256

   116 2/3

   16

   14 7/12

   1 31/144

   1

   1/100

   1/112

   1/2000

   1/2240

   short hundredweight

   700000

   35000

   29166 2/3

   25600

   11666 2/3

   1600

   1458 1/3

   121 19/36

   100

   1

   25/28

   1/20

   5/112

   long hundredweight

   784000

   39200

   32666 2/3

   28672

   13066 2/3

   1792

   1633 1/3

   136 1/9

   112

   1 3/25

   1

   7/125

   1/20

   short ton

   14000000

   700000

   583333 1/3

   512000

   233333 1/3

   32000

   29166 2/3

   2430 5/9

   2000

   20

   17 6/7

   1

   25/28

   long ton

   15680000

   784000

   653333 1/3

   573440

   261333 1/3

   35840

   32666 2/3

   2722 2/9

   2240

   22 2/5

   20

   1 3/25

   1

   Now be amazed how few numbers you need to remember to measure the same range of the same quantities (length, volume, mass) in the metric system:

   Prefix	Symbol	In Words	Shift Point	From	To
   micro	µ	a millionth	6	<—	—>
   milli	m	a thousandth	3
   centi	c	a hundredth	2
   deci	d	a tenth	1
   deca	da	ten	1	—>	<—
   hecto	h	a hundred	2
   kilo	k	a thousand	3
   mega	M	a million	6

   As there is only one unit of measurement per quantity, conversions between units are merely conversions between prefixes. Once you can convert one prefix to another, you can practically convert all SI units among each other.

   For volume and mass, there are two additional customary metric units except the standard units, but these are really only shortcuts for standard units: The liter is nothing else but a cubic decimeter, and the ton nothing else but a megagram.

   So how to convert between these prefixes?

   Just shift the decimal point - no math required!

   To convert for example 1852 meters to kilometers, just shift the decimal point 3 places left = 1.852 kilometers! A snap! To convert back, just shift 3 places back right again. Even to convert across prefixes is no deal at all: Convert 160934.4 centimeters to kilometers by first shifting the point 2 places left from centi, then another 3 places left to kilo = 1.609344 kilometers, done! Just imagine in comparison to convert inches to miles - you'd have to divide by 63360!

   So — which of the two sets of tables would you rather learn by heart and use? An insane chaos of arbitrary fractions which you have to multiply and divide by, or a systematic scheme needing only shifts of the decimal point!

   And this is not all: The English units only cover a very limited range of measurement — for length the smallest unit you get is the mil, the largest the league.

   The prefix system allows you to size up or down metric units to almost any size you possibly ever need — without having to know special unit names for each and every physical quantity. Learn the prefixes once, and they work for every possible unit. This is the complete table:

   Prefix	Symbol	In Words	Shift Point	From	To
   yocto	y	a septillionth	24	<—	—>
   zepto	z	a sextillionth	21
   atto	a	a quintillionth	18
   femto	f	a quadrillionth	15
   pico	p	a triillionth	12
   nano	n	a billionth	9
   micro	µ	a millionth	6
   milli	m	a thousandth	3
   centi	c	a hundredth	2
   deci	d	a tenth	1
   deca	da	ten	1	—>	<—
   hecto	h	a hundred	2
   kilo	k	a thousand	3
   mega	M	a million	6
   giga	G	a billion	9
   tera	T	a triillion	12
   peta	P	a quadrillion	15
   exa	E	a quintillion	18
   zetta	Z	a sextillion	21
   yotta	Y	a septillion	24

   As you can see, it doesn't really get more complicated - only you have more possibilities!

   In fact, as the English system was designed to master nothing more than medieval measurement tasks, and also lacks the capability of systematic extension like the prefixes of the metric system, the English system fails to provide suitable units for numerous modern measurements. So wavelength of light, power of radiation, mass of blood cells and many more have to be measured in metric units, isn't that funny?

3. Decimal system

   The decimal system is nothing new - you use it every day when you deal with money. Something might cost 4.98 Dollars or 0.45 Dollars.

   The decimal system is superior to the fractional system, because

   1. You can immediately see which of two values is greater. While you can readily see that for example 0.33 Dollars is greater than 0.31 Dollars, you have to twist your brain to figure out that 1/3 (= 0.33) inch is greater than 5/16 (= 0.31) inches. Or, take three imperial drill bits: the 5/32, the 1/8 and the 9/64 - and take the equivalent metric drill bits: the 4.0, the 3.0 and the 3.5 - wouldn't you agree that the metric specification makes the drill sizes clear and evident, letting you readily see not only which one's the biggest or the smallest, but also by how much each drill is bigger than the other - while with the English specification you have to tie a knot into your brain to figure out not only which one's the biggest, but let alone imagining the sizes of the drills?
   2. You can easily add and subtract decimal numbers. It's a snap to add 0.33 Dollars plus 0.31 Dollars = 0.64 Dollars! But add 1/3 inch and 5/16 inches and find the result to be a confusing 31/48 inches! (and - would you know how to get to this result?) How about subtracting them: 0.33 Dollars minus 0.31 Dollars is simply 0.02 Dollars, while 1/3 inch minus 5/16 inches equals 1/48 inch! Imagine things in the supermarket were sold by fractions of a Dollar: You have one Dollar, and you want to buy a pound of bananas and one of apples. Bananas are 5/8 Dollars a pound while apples are 1/3 Dollar. Can you buy both? Now that you will agree that this would be a braindamaged system to measure prices in, yet you use it to measure length, volume, mass and many more things! Disregarding the fact that it's a pain in the neck to add or subtract fractions, most people wouldn't even know how to do it!
   3. Each number has exactly one decimal representation. While you write 0.4 in decimal, with fractions you can write 2/5, 4/10, 6/15 etc. etc. making it obscure to identify equal values. Sure, 9/64 plus 7/64 is 16/64, but don't forget that 16/64 is actually the same as 8/32, 4/16, 2/8 and, eventually 1/4!
   4. Decimal is native to measurement, as it makes the value's precision evident. Every measurement involves precision. Say the length of a fence is 45.413 meters, but not for every job you need to know the value so exactly - e.g. depending on if you actually want to replace the fence with the exact same size new one and have it cut in the shop, or you just want to have rough idea to estimate how much paint you need, you can say either 45.413 m, 45.41 m, 45.4 m or just 45 m, making it clear that the measurement is to a millimeter's, a centimeter's, a decimeter's or just a meter's precision.

   You already use the decimal system for calculating with money - so you know it anyway! As it's the easier system, why not forget all the convoluted fractions and just use decimals!