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60 free Metric System trivia questions with answers — science & nature quiz, new questions added Aug 2026.
Almost every country on Earth measures in metres, kilograms and litres, yet few people know where those units came from or how they are defined today. This quiz covers the whole story of the metric system: the chaos of pre-revolutionary French measures, the survey from Dunkirk to Barcelona that fixed the metre, Napoleon's retreat to the mesures usuelles, the 1875 Metre Convention, the platinum-iridium prototypes, the birth of the SI in 1960, the 2019 revision that tied every base unit to a constant of nature, and the long, unfinished metrication of the United States and Britain. Easy questions ask how many base units the SI has and what prefix means a thousand; harder ones cover the newest prefixes, the Kibble balance, the Gimli Glider and why the kilogram is the only base unit with a prefix built in. It suits science students, engineers, teachers, and quiz nights that want a science round with a bit of history in it. Every answer has been checked against the Wikipedia articles on the metric system, the SI, its units and its history, and each question shows its source once you have answered.
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Q 01How many base units does the modern International System of Units (SI) have?
Seven
They are the metre, kilogram, second, ampere, kelvin, mole and candela; everything else, from the newton to the tesla, is derived from them.
Q 02The metric prefix "kilo" multiplies a unit by what factor?
1,000
"Milli" divides by the same factor, so a milligram is a thousandth of a gram.
Q 03What is the process of adopting the metric system called?
Metrication
The SI has been adopted as the official system of weights and measures in almost every country in the world.
Q 04Besides America, which two countries did NIST identify as lacking mandatory metric laws?
Liberia and Myanmar
Both have since announced moves toward the metric system, with Liberia pledging to adopt it in 2018.
Q 05The metric system was formally defined in French law on 7 April of which year?
1795
The same decree fixed the gram as the weight of a cubic centimetre of water at the temperature of melting ice.
Q 06On the eve of the Revolution, roughly how many different units of measure were in use across France?
About 800
Because each unit could differ from town to town, they had up to a quarter of a million different definitions.
Q 07The 1791 definition of the metre made it one ten-millionth of the distance from the equator to what?
The North Pole
In practice the length was fixed by surveying the arc of the Paris meridian between Dunkirk and Barcelona.
Q 08Which two astronomers surveyed the meridian arc from Dunkirk to Barcelona to fix the length of the metre?
Méchain and Delambre
The job was expected to take two years and took more than six, from 1792 to 1798, amid the chaos of the Revolution.
Q 09Which French abbot proposed in 1670 a decimal system of length based on the Earth's dimensions?
Gabriel Mouton
His unit, the virgula, could be reproduced anywhere with a pendulum that beat 3,959.2 times in half an hour.
Q 10Which British inventor called in 1783 for a global decimal measurement system based on water's density?
James Watt
He was struggling to communicate with German scientists; five years later a French chemist commissioned decimal brass cylinders for his own experiments.
Q 11Which chemist defined the gram with René Just Haüy before the kilo prefix was added in 1792?
Antoine Lavoisier
The result is that the kilogram is the only SI base unit with a prefix built into its name.
Q 12What was Napoleon's 1812 hybrid measurement system with old customary names called?
Mesures usuelles
The metric system was reimposed by the 1837 Assembly and took effect again in 1840.
Q 13The Metre Convention was signed in Paris on 20 May 1875 by representatives of how many nations?
17
The signatories ranged from Argentina and the Ottoman Empire to the United States and Venezuela.
Q 21The SI was launched by the CGPM in which year, initially with six base units?
1960
The mole was added as the seventh base unit later, in 1971.
Q 22The second has been defined since 1967 by the hyperfine transition frequency of which atom?
Caesium-133
The number is exactly 9,192,631,770 cycles per second, and a good caesium clock can detect a 2 cm change in altitude by gravitational time dilation.
Q 23One mole contains exactly how many elementary entities?
6.02214076 × 10^23
That figure is the Avogadro number, and it was fixed as an exact value in the most recent SI revision.
Q 14The international prototypes of the metre and kilogram were made of platinum alloyed with which metal?
Iridium
The 90/10 alloy is exceptionally hard; the London firm Johnson Matthey delivered 30 metre bars and 40 kilogram cylinders.
Q 15The prototype metre bar had a special X-shaped cross section, named after which engineer?
Tresca
The shape minimised torsional strain during length comparisons; the kilograms were simple cylinders.
Q 16The International Prototype of the Kilogram, Le Grand K, defined the kilogram from 1889 until which year?
2019
It sits under three bell jars in a vault near Paris that takes three independently controlled keys to open.
Q 17How many times was the IPK formally compared with its official copies during its 130-year reign?
Three
The verifications of 1889, 1948 and 1989 showed the copies drifting apart by about 50 micrograms.
Q 18The 2019 SI revision defines the kilogram by fixing the exact value of which quantity?
The Planck constant
The Kibble balance, called the watt balance until 2016, lets laboratories realise the unit without any artefact.
Q 19Since 1983 the metre has been the distance light travels in what fraction of a second?
1/299,792,458
This definition replaced one based on the wavelength of a spectral line; it fixes the speed of light exactly.
Q 20Before the 1983 light-speed definition, the metre was defined by light from which element?
Krypton-86
Before that, from 1889, the standard was a platinum-iridium bar kept near Paris.
Q 24The kelvin was formally added to the SI in 1954 by defining 273.16 K as the temperature of what?
The triple point of water
It is now defined instead by fixing the Boltzmann constant.
Q 25The Celsius scale was known in English by what name until it was renamed in 1948?
Centigrade
The change honoured Anders Celsius, whose 1742 original ran the other way, with 0 at boiling and 100 at freezing.
Q 26In which year did an international convention at an exposition establish the ampere as the unit of current?
1881
It honours André-Marie Ampère, considered a father of electromagnetism alongside the Dane Hans Christian Ørsted.
Q 27The candela is the SI unit of what?
Luminous intensity
A common wax candle gives out roughly one of them.
Q 28A litre is exactly equal to which volume?
One cubic decimetre
The word comes from the litron, an old French unit that itself descended from a Byzantine Greek unit of weight, not volume.
Q 29From 1901 to 1964 the litre was defined not as a cube but as the volume of what?
One kilogram of pure water at maximum density
That made the old litre about 1.000028 of the modern one, a discrepancy finally abolished in 1964.
Q 30A hectare is the area of a square with sides of what length?
100 metres
It equals 100 ares, the original unit of 100 square metres from the first metric law, and there are 100 hectares in a square kilometre.