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Who invented the metric system?

by Pat Naughtin 2009

The answer to this question comes in four parts. The metric system's three separate parts were developed at three different times and in three different places. Then they were all put together at a fourth time. This is easily seen when we give the metric system its first full name. In 1790, it was called the:

decimal metric system

Let's work backwards through these three words.


An English bishop, John Wilkins, (1614-1672) invented the system part of the decimal metric system when he published a book with a plan for a 'universal measure' in 1668. To be more exact, Bishop Wilkins released his plan for what became the decimal metric system on Monday, 1668 April 13 when the Royal Society published 'AN ESSAY Towards a REAL CHARACTER, And a PHILOSOPHICAL LANGUAGE'.

I think that it is fair to say that John Wilkins 'invented' the system we now use in the dictionary sense of the word invented (invent: to create by thought, originate, new method, ... Australian Concise Oxford Dictionary) because, although the parts had been around for a while, it was Wilkins' plan for a system that could be used to measure all things based on a single universal measure, that was completely new.

Bishop John Wilkins was, among other things: Warden of Wadham College, Oxford; Master of Trinity College, Cambridge; married to Oliver Cromwell’s sister; writer of the first book in English on secret codes; writer of one of the first science fiction books about a trip to the Moon; and convener and chairman of the first meeting of the Royal Society, still one of the world's most important science academies.

Wilkins' short proposal for a 'universal measure' in 1668 contained almost all the elements of the International System of Units (SI), the modern metric system. Wilkins devised a decimal system with a universal standard of length, preferably based on accurately measuring the Earth or time, and wrote that this standard length could then be used to define area, volume, and 'weight'* using distilled rainwater. However, Wilkins did not use the word metre and he did not use metric prefixes; these ideas came later.

Another invented component of our metric system was the concept of prefixes to make it possible for a few simple metric units to measure from the smallest (sub-atomic) to the largest objects in the Universe.

The original idea for the metric prefixes came from the French military engineer, Prieur de la Côte d'Or, who suggested the metric prefixes for a tenth (deci) and a hundredth (centi) before 1795. Jan Hendrik van Swinden (1746/1823), a Dutch mathematician, further developed Prieur's prefixes into seven with Greek prefixes for multiples and Latin prefixes for subdivisions, of the various units. Later, in 1874, more prefixes were added at the suggestion of the British Association for the Advancement of Science (BAAS) and this is probably why so many of them have English or Scottish names such as joule and watt. These then became the basis for our current range of 20 prefixes.

(* Note that Wilkins used the word weight, as Isaac Newton, who was a student at Trinity College Cambridge when John Wilkins was Master, had not yet shown how weight and mass are two different things. Isaac Newton did not explain the difference between weight and mass until he published his famous book, Principia, in 1687. By then Newton was a mathematics professor at Trinity College, Cambridge.)


The word, metre, and its adjective metric, probably derived from a translation of Wilkins' words, 'universal measure', into the Italian (Latin) words, 'metro cattolico', by Tito Livio Burattini who was born in Italy but spent most of his life in Poland, where he worked as an architect. He had previously travelled to study the building methods used in ancient Egypt.

Burattini published a book called, Misura Universale, in 1675, that first used the words, metro cattolico. Both Misura Universale and metro cattolico mean universal measure. On the title page of his book, Burattini wrote:

Treatise in which it is shown how in every Place of the World it is possible to find a UNIVERSAL MEASURE & WEIGHT having no relation with any other MEASURE and any other WEIGHT & anyway in every place they will be the same, and unchangeable and everlasting until the end of the WORLD.

The Italian word, metro, that became mètre in France, metre in England, and meter in the USA, was before that a Greek word metron that meant a measure. The word mètre was probably chosen in France in the 1780s because Jean Charles de Borda argued vigouously that the single word, mètre, should be used instead of an expression like John Wilkins' universal measure.


The decimal part is the oldest of the three. Decimal numbers have been used on and off since ancient times in many parts of the world, but they never became well established for long periods. It may be that our decimal measuring system automatically arose because our counting numbers are based on the simple fact that we have ten fingers that we use for counting. One early example was that of the Roman army, which was divided into groups of 100 soldiers led by a Centurion but the Romans also counted in fives, twelves (dozens), and twenties and divided smaller portions in to twelfths.

Our modern numbers are sometimes called Indian/Arabic numbers because Arab scholars learned of the numbers 1, 2, 3, 4, 5, 6, 7, 8, 9 and 0 from the Indian people through the work of Al-Khwarizmi. Latin translations of Al-Khwarizmi's works spread to Europe after Adelard of Bath translated them in the early 12th century. However, European people only gradually saw the value of using decimal calculating methods.

The first person to fully recognise the importance of decimal numbers, and of how they could be used to simplify arithmetic in all areas of commerce, engineering, science, surveying, and for decimal currency, was Simon Stevin, from Brugge in Flanders (now in Belgium).

Simon Stevin was an engineer, a surveyor, and an accountant. While he was developing a set of tables for working out the amount of interest that banks should charge for lending money, he realised that decimal numbers made all of these money calculations much easier to do, and then he also realised that decimal numbers could also make all the calculations in all the other areas of his life, including lengths and angles for engineering and surveying, much easier as well. Simon Stevin believed that the use of decimal numbers could rid the world of the cumbersome common, or vulgar, fractions with all of their various calculating difficulties. Simon Stevin published his decimal ideas in a book called, 'Disme: the art of tenths' in 1585, and this book influenced John Wilkins, who had read Stevin's book (either in the original Flemish or in an English translation after 1608) before he decided on decimal numbers for his system of 'universal measure' in 1668. Thomas Jefferson also read Simon Stevin's book and it is possible that the dime, a tenth of a dollar in the USA, was named after Simon Stevin's book Disme: the art of tenths.

Although Simon Stevin recognised the ease of decimal calculations it is not true to say that he invented them. What he did with his books and his demonstrations was to successfully promote the use of decimal numbers in many areas where they had not been used previously.

système métrique décimal

The first time that the three parts of the metric system came together, they were written in French as shown above.

It was written like this because the people who were developing the idea for a legal 'universal measure' in the 1780s usually wrote or spoke to each other in the French language.

Whenever Sir John Riggs-Miller, from England; Benjamin Franklin and Thomas Jefferson from the USA met together or corresponded on a proposal for a 'universal measure' with Charles Maurice de Talleyrand-Périgord, (usually known simply as Talleyrand) and Jean-Antoine Nicolas de Caritat, Marquis de Condorcet (usually known simply as Condorcet) from France they did so using the French language.

Benjamin Franklin was USA Ambassador to France from 1776 to 1784 and Thomas Jefferson served in this position from 1784 till 1789. Condorcet and Jefferson were particularly close friends and it seems likely that Franklin and Jefferson promoted their strong support for decimal measurement and for decimal currency during the 1770s and the 1780s.

Essentially, Talleyrand, Condorcet, Riggs-Miller, Franklin, and Jefferson were proposing that their three nations — France, England, and the USA — should cooperate to equalise their weights and measures by the joint introduction of a 'système métrique décimal' (decimal metric system).

In the 1780s, they had all realised that the money and measuring methods were a mess in all three nations. For example, in the USA, various currencies in use came from the various nations who had an interest in the USA. There were such things as Pounds from the UK, Guilders from the Netherlands, Pieces of Eight and Reals from Spain, and this mess had been recognised by Thomas Jefferson as early as 1782, when he suggested the use of a decimal currency for the USA and achieved agreement among the states on this, in principle, by 1785.

Jefferson's decimal currency system had been already well established in the thirteen states of the USA by the daily use of Benjamin Franklin's independently minted, 'Fugio Cent' that started in 1787. Decimal currency became a reality when George Washington and Thomas Jefferson combined their political forces to pass the USA Congress Mint Act in 1792. The world's first decimal currency, with one dollar consisting of 100 cents, was introduced smoothly and successfully to the USA. I believe that the ready acceptance of decimal currency in the USA had a major influence on the measurement leaders in France, who were developing the decimal metric system to become the legal French measuring system.

When was the decimal metric system invented?

As we have seen, the three parts of the decimal metric system were originally developed in 1585, 1668, and 1675. Then the three parts were put together in several different places at a fourth time.

The crucial time in the combination of the various ideas that formed the decimal metric system mostly came together in the year 1790. Here is a timeline of important relevant events that took place that year:

1790 January 8

George Washington (1732/1799), in his first annual message to Congress, reminded the legislators of their responsibility on weights and measures when he said:

A uniformity of weights and measures is among the important objects submitted to you by the Constitution, and, if it can be derived from a standard at once invariable and universal, it must be no less honorable to the public council than conducive to the public convenience. ... Uniformity in the currency, weights, and measures of the United States is an object of great importance, and will, I am persuaded, be duly attended to.

George Washington repeated his call for uniformity in the currency, weights, and measures of the United States of America with similar calls for action in his second and third annual presidential messages to congress (later these annual reports became known as the 'State of the Union Address').

George Washington was clearly referring to an idea similar to Wilkins' 'universal measure' when he said, 'derived from a standard at once invariable and universal'.

The Congress accepted that decimal currency had been agreed between the states in 1785 but that uniform standard measures remained a problem. The USA Congress discussed which weights and measures to use for the USA and then responded to George Washington's speech by asking Secretary of State, Thomas Jefferson, to make a special report on the subject of measurement for the USA. They had the authority to decide on a standard of weights and measurement as a Constitutional right, under Article I, Section 8.

1790 March 29

Sir John Riggs Miller had previously raised difficulties arising from the use of multiple measures in the British Parliament where he was quoted as saying that disorganised measures led to:

... the perplexing of all dealings, and the benefitting of knaves and cheats.

Knowing that Sir John Riggs Miller had raised the question of weights and measures in the British House of Commons during 1789, Talleyrand, Bishop of Autun, wrote this private letter to him. This is Sir John Riggs Miller's translation of Talleyrand's letter.


I understand that you have submitted for the consideration of the British Parliament, a valuable plan for the equalization of measures: I have felt it my duty to make a like proposition to our National Assembly. It appears to me worthy of the present epoch that the two Nations should unite in their endeavour to establish an invariable measure and that they should address themselves to Nature for this important discovery.

If you and I think alike on this subject, and that you are of opinion that much general benefit may be derived from it, it is through you only that we can hope for its accomplishment; and I beg to recommend it to your consideration. Too long have Great Britain and France been at variance with each other, for empty honour or for guilty interests. It is time that two free Nations should unite their exertions for the promotion of a discovery that must be useful to mankind.

I have the honour to be, Sir, with due respect, your most humble and obedient servant,

The Bishop of Autun

Talleyrand's proposals for a new measuring method were based on a survey he had done on the measures currently in use in France. The mess they were in can be gauged from this quote from The Measure of Enlightenment By J. L. Heilbron:

The existence of French men and women around 1790 was made miserable by, among other things, 700 or 800 differently named measures and untold units of the same name but different sizes. A 'pinte' in Paris came to 0.93 litre; in Saint-Denis, to 1.46; in Seine-en-Montagne, to 1.99; in Précy-sous-Thil, to 3.33.

The aune, a unit of length, was still more prolific: Paris had three, each for a different sort of cloth; Rouen had two; and France as a whole no fewer than seventeen, all in common use and all different, the smallest amounting to just under 300 lignes, royal measure, the largest to almost 600.

France possessed non-uniform measures in law as well as by custom. Their multiplicity went with other relics of the feudal system, which maintained arbitrary rents and duties usually to the disadvantage of the peasant.

A landlord wanted his bushels of grain or hogsheads of beer in the biggest measures in use in the neighborhood, and he preferred to sell according to the smallest. Nor were all seigneurs above enlarging the vessel in which they collected their rents; and since in many cases they possessed the only exemplars of their patrimonial bushel, no one could be certain that it did not grow in time. But one suspected.

A frequent complaint in the cahiers, or notebooks of desiderata brought by representatives of the people to the meeting of the Estates General in 1789, was that 'the nobles' measure waxes larger year by year. These same representatives castigated the oppressive confusion of customary measures as barbaric, ridiculous, obscurantist, gothic, and revolting, and demanded an end to them, and the establishment of a system of unchanging and verifiable weights and measures throughout the country, or at least throughout their region. Many urged that the King's measure, the royal foot, be made the law of the land.

Sharpers and crooks whose practices were not sanctioned by ancient rights and wrongs and middlemen acting in analogy to money changers opposed the rationalization that menaced their livelihood.

Talleyrand's concept was for the adoption of a brand new basic standard, 'derived from nature' (pris dans la nature) and therefore acceptable to all nations. Talleyrand further suggested that the French National Assembly, the English Parliament, and the Royal Society of London should undertake preliminary work towards this objective jointly. He wrote:

Perhaps this scientific collaboration for an important purpose will pave the way for political collaboration between the two nations.

1790 April 13

Sir John Riggs Miller reported to Parliament on the receipt of the letter from Talleyrand, and expressed himself in favour of the scheme. He then made a speech to the British House of Commons proposing extensive measurement reform. Riggs Miller had been in contact with both Talleyrand in France and with Thomas Jefferson, who was then the first Secretary of State of the United States of America.

1790 April 17

Talleyrand, one of the foremost members of the French National Assembly, introduced the subject and launched a debate on measurement. His report to the Assembly included a detailed analysis of the extremely muddled state of French weights and measures. Talleyrand proposed to the National Assembly a decimal system of stable, unvarying and simple measurement units. These were to be based on the length of the seconds pendulum at 45° North latitude beating a second.

At Talleyrand's suggestion, the French National Assembly adopted this new measuring system. Louis XVI authorised scientific investigations aimed at reform of all French weights and measures and these investigations led to the development of the 'decimal metric system' as the legal measurement system, firstly in France with the passage of several laws mostly in the 1790s, and then in the rest of the world. Talleyrand also suggested that the Academy of Sciences in Paris collaborate with the Royal Society of London in defining the new measuring unit.

A French politician, La Rochefoucault, had this to say in the National Assembly in support of Talleyrand's proposal:

We cannot make enough haste over promulgating this decree, which should bring about fraternal relations between France and England.

The French National Assembly and subsequently Louis XVI approved of Talleyrand's proposal. As a result, even though it was in the middle of the French revolution, the National Assembly of France requested the French Academy of Sciences to deduce an invariable standard for all the measures and all the weights and to prepare a report on the development of a system of measurement for France and for the world. The French National Assembly then sent delegates to Britain, Spain and the USA to propose cooperation in developing a universal system of units for measurement.

1790 May 8

Talleyrand sent Sir John Riggs Miller a copy of the National Assembly's minute of May 8 referring to the new measurement arrangements. In this minute the French king, Louis XVI, was asked to write to the British king, George III, inviting joint action to determine a natural standard of weight and measure. However, subsequent historians have not been able to find such a letter in the Royal Archives at Windsor Castle.

1790 July 13

Thomas Jefferson reported back to the Congress with a 'Plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States'. You can find full details of Jefferson's plan at: http://avalon.law.yale.edu/18th_century/jeffplan.asp and at http://ourworld.compuserve.com/homepages/Gene_Nygaard/t_jeff.htm

In the first paragraph of his report, Jefferson provides evidence of the international effort to develop a decimal metric system between France, the UK, and the USA. Thomas Jefferson wrote:

... on the 15th of June, came to my hands, from Paris, a printed copy of a proposition made by the Bishop of Autun, to the National Assembly of France, on the subject of weights and measures; and three days afterwards I received, through the channel of the public papers, the speech of Sir John Riggs Miller, of April 13th, in the British House of Commons, on the same subject.

Thomas Jefferson's report carried considerable influence in the Congress of the USA as he was the first Secretary of State of the USA for President George Washington, but no official action was taken and the Congress passed no legislation relating to weights and measures as a result of Jefferson's report.

Jefferson's report used some of the scientific investigations aimed at reform of the French weights and measures but it varied in the detail. Jefferson's proposals also had a remarkable similarity to the design for a 'universal measure' outlined by John Wilkins in 1668. It seems likely that Jefferson had access to: 'An Essay Towards a Real Character and a Philosophical Language (1668) by John Wilkins'. This conjecture seems more likely when we compare Wilkins' plan for length with that of Jefferson.

Wilkins' Essay 1668 April 13Jefferson's Report 1790 July 13
Let this Length therefore be called the Standard; let one Tenth of it be called a Foot; one Tenth of a Foot, an Inch; one Tenth of an Inch, a Line. And so upward, Ten Standards should be a Pearch; Ten Pearches, a Furlong; Ten Furlongs, a Mile; Ten Miles, a League, & c.Jefferson defined a standard length using a seconds pendulum then he wrote: Let the foot be divided into 10 inches; the inch into 10 lines; and the line into 10 points. Let 10 feet make a decad; 10 decads one rood; 10 roods a furlong; and 10 furlongs a mile.

And there are many other parallels. In many respects Jefferson's plan might have been taken straight from John Wilkins' essay with only slight changes to the names of the various components of the plan and a few minor differences. For example Jefferson suggested a pendulum that had a rod instead of a string. Details of Wilkins' plan can be found at: http://www.metricationmatters.com/docs/CommentaryOnWilkinsOfMeasure.pdf and a Wikipedia article on Jefferson's decimal plan can be found at: http://en.wikipedia.org/wiki/Plan_for_Establishing_Uniformity_in_the_Coinage,_Weights,_and_Measures_of_the_United_States

Note: I have been unable to definitely confirm that Jefferson had access to Wilkins' Essay. Jefferson was a very keen book collector and I, and several very helpful librarians, have searched many catalogs of his extensive collections. I suspect that he either owned or had access to Wilkins' Essay, and that possibly his copy of Wilkins' book was lost in the Library of Congress fire of 1851, (http://www.loc.gov/exhibits/jefferson/jefflib.html )

Jefferson recommended a two-part decimal plan to Congress. The first part of Jefferson's plan proposed the adoption of a universal length based on the seconds pendulum, measured at 45 degrees North latitude at sea level and the changing of existing old English units to this new universal measure.

The second part of Jefferson's plan proposed the use of a decimal system as a basis for dividing and multiplying the seconds pendulum unit to reduce:

... every branch to the same decimal ratio, thus bringing the calculations of the principal affairs of life within the arithmetic of every man who can multiply and divide plain numbers.

1790 August 22

The French King Louis XVI authorized scientific investigations aimed at a reform of French weights and measures. Talleyrand's proposal, having been referred to the Committee on Agriculture and Commerce, was recommended to the king, who sanctioned action on August 22.

This was the French decree that led to the further development of the metric system. The French Academy of Sciences was made responsible, and appointed a committee that consisted of: Jean Charles de Borda (1733-1799), Joseph-Louis Comte de Lagrange (1736-1813), Pierre-Simon Laplace (1749-1827), Gaspard Monge (1746 -1818), and Marie Jean Antoine Nicholas Caritat, the Marquis de Condorcet (1743-1794). Their first report, in October, recommended the decimal division of money, weights, and measures. However, it should not be inferred that this was a smooth or an easy process. Stephen Hawking in his book, God created the integers, describes Laplace's contribution to the metric system as follows:

Engrossed as he was in science, Laplace had little time for the tumult of politics in the late 1780s and early 1790s. He took no part in the affairs of the French Revolution during its most radical phase in the early 1790s, except to participate in the committee that devised the metric system, part of a systematic attempt to overthrow the shackles of the Old Regime. One camp argued that the fundamental unit of length should be defined in terms of the earth's equatorial circumference.

Laplace argued, instead, that given the role of the right angle in geometry, the fundamental unit of length should be based on the length of the quadrant from the North Pole to the equator. Thanks to Laplace's successful argument, the meter was defined as 1/10 000 000th of the distance from the pole to the equator. By the end of 1793 the political atmosphere in Paris became too intemperate for Laplace. Along with many other leading scientists, including Lavoisier and Coulomb, Laplace was purged from the committee devising the metric system. The radical republicans loudly announced that such responsibilities could only be entrusted to men known for 'their Republican virtues and hatred of kings'.

Literally fearing for his neck, Laplace and his family fled from Paris to the country town of Melun, thirty miles (50 kilometres) away. In retrospect, Laplace had correctly judged the probabilities of the possible outcomes. His friend and colleague, the chemist Antoine Lavoisier, chose to remain in Paris, where he lost his head to the guillotine in the spring of 1794.

The National Assembly decreed that all measures in use throughout the provinces of France should be sent to the Academy of Sciences who would then issue new standard measures to all the parishes of France. The idea was that the old measures could be dispensed with within six months.

1790 October 27

The French Academy of Science issued a report that recommended the decimal division of French money along similar lines to those used in the USA and:

... that the length of a meridian from the North Pole to the Equator be determined, that 1/10 000 000th of this distance be termed the metre and form the basis of a new decimal linear system, and, further, that a new unit of weight should be derived from the weight of a cubic metre of water.

The committee specifically rejected the seconds pendulum as a standard for length. Their report also recommended that the new system of weights and measures should be decimal and they included a list of prefixes for decimal multiples and sub-multiples.

At this point all of the components were in place for the decimal metric system that later became the International System of Units (SI) that we now use in every nation in the world.

Later developments included more units, more prefixes, better definitions, and the development of a property called coherence between all units. The latest version of the modern metric system, approved in 1960, is called the Système International d'Unité (SI) in French or the International System of Units (SI) in English. Note that the initials SI are the same for both French or for English.

1790 November 11

Talleyrand again urged that the preparation of a new system of weights and measures should be a collaborative venture, by inviting the participation of the English Parliament and the Royal Society of London. Talleyrand also made efforts to establish contacts with other countries, including negotiations with Thomas Jefferson concerning the definition of the metre. Jefferson initially favored using a pendulum at the latitude of 38°N as this was close to the centre of the USA, but eventually he accepted the 45°N, as he felt that this was better suited to an international future for the decimal metric system.

At the end of 1790, the Académie des Sciences Française appointed a scientific commission to reconsider the whole question of measurement. They were: Lagrange, Laplace, Borda, Monge, and Condorcet. In their report to the Academy, the scientific commission reconfirmed that the new unit of length be one ten-millionth of the distance at sea level from the pole to the equator. One of the reasons that they chose the quadrant was because one of the commission members, Jean-Charles De Borda, had constructed extremely precise graduated circles for measuring angles — exactly the kind required for this sort of work. Borda's circles were graduated in units called 'grads' with 100 centesimal grad divisions to a quadrant. Borda sneered at the Babylonian degrees used by others as too old-fashioned (in 1790!) to be used for the development of the modern decimal metric system.

The secretary of this scientific commission was Jean-Antoine Nicolas de Caritat, Marquis de Condorcet who as stated earlier is usually known simply as Condorcet. It was Condorcet who said that the metric system was:

For all time, for all people


John Wilkins


ito Livio Burattini


Simon Stevin


The Measure of Enlightenment


Outlines of the Evolution of Weights And Measures and the Metric System

by William Hallock Ph.D. and Herbert T. Wade (Macmillan And Co. Ltd. London 1906)

You can find a comprehensive metrication timeline at http://www.metricationmatters.com/docs/MetricationTimeline.pdf and this is just one of the many resources that you will find on the Metrication matters website at http://metricationmatters.com that will help you with your own metrication upgrade.

© Pat Naughtin 2009

Pat Naughtin helps people understand how to go about their metrication upgrade —quickly and easily — by helping them avoid mistakes that he has made himself, or that he has seen made by others during his more than 40 years of involvement with metrication matters.

Pat specialises in the modern metric system based on the International System of Units (SI), but he is mostly concerned with the processes that people use for themselves, their groups, their businesses, their industries, and their nations as they go about their inevitable metrication process.

Pat Naughtin is a highly knowledgeable metric enthusiast, who is also a writer, professional speaker, editor, and publisher.

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