Metric System Trivia
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107 free Metric System trivia questions with answers — science & nature quiz, new questions added Oct 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.
30 of 107 questions with answers and explanations. Play the quiz
Q 01Which of these quantities is measured by one of the seven SI base units?
Time
Time. Its unit, the second, was once a set fraction of the Earth's day, but the planet's spin proved too unsteady, so since 1967 atomic clocks have defined it.
Q 02The metric prefix "kilo" multiplies a unit by what factor?
1,000
1,000. Computing muddied it by calling 1,024 bytes a kilobyte, so in 1998 a separate prefix, kibi, was coined to leave kilo meaning exactly a thousand.
Q 03Since a six-nation agreement in 1959, which American unit of length has been defined as exactly 0.9144 metres?
The yard
The yard. English-speaking nations had slightly different yards, so to agree on one value the American yard was shortened and the British one lengthened.
Q 04A popular myth says the United States and which two other countries are the last holdouts against the metric system?
Liberia and Myanmar
Liberia and Myanmar. NIST calls it a myth spread by an old CIA Factbook list: every country has adopted the SI, and even US feet and inches are officially defined in terms of the metre.
Q 05The 1795 law that defined the metre and gram also introduced which unit of currency?
The franc
The franc. The same reform swept away royal money too: the old livre was exchanged for the new currency at 81 livres to 80 francs.
Q 06On the eve of the Revolution, roughly how many different units of measure were in use across France?
About 800
About 800. Each could change from town to town and even from trade to trade, so by one estimate they hid a quarter of a million different local measures.
Q 07The 1791 definition of the metre made it one ten-millionth of the distance from the equator to what?
The North Pole
The North Pole. Surveyors could measure only a stretch of that line and scale it up, and the metre they produced was later found to be about 0.2 mm short.
Q 08In medicine and engine sizes, one 'cc' is exactly the same volume as one what?
Millilitre
Millilitre. A cc is a cubic centimetre, which is why a 5 cc syringe holds 5 ml and a 750 cc motorbike engine displaces three-quarters of a litre.
Q 09Which British inventor called in 1783 for a global decimal measurement system based on water's density?
James Watt
James Watt. He was tired of converting the pounds and ounces in German chemists' reports, which changed from one part of the empire to the next.
Q 10Which chemist worked with René Just Haüy in 1793 to define the grave, the unit that became the kilogram?
Antoine Lavoisier
Antoine Lavoisier. He and Haüy made the measurements that fixed the unit, the year before Lavoisier was sent to the guillotine.
Q 11Which French ruler rolled back the metric system, letting shopkeepers use the old pound and foot again?
Napoleon
Napoleon. His 1812 'mesures usuelles' kept the familiar names but tied them to metric sizes, so a livre became exactly 500 grams, and France went fully metric again only in 1840.
Q 12An 1875 measurement treaty's signing date, 20 May, is marked as what?
World Metrology Day
World Metrology Day. The kilogram's new definition took effect on that day in 2019, and UNESCO made it an official international day in 2023.
Q 13The international prototypes of the metre and kilogram were made of platinum alloyed with which metal?
Iridium
Q 21Chemistry's constant 6.02214076 × 10^23 is a number named after which Italian scientist?
Amedeo Avogadro
Amedeo Avogadro. He never knew the figure: it was named in his honour in 1909, half a century after his death, by the physicist Jean Perrin.
Q 22In 1954 the kelvin was defined by fixing 273.16 K as the temperature of what?
The triple point of water
The triple point of water. It is the one temperature at which ice, liquid water and vapour all coexist; since 2019 the kelvin has instead been defined by fixing the Boltzmann constant.
Q 23The Celsius scale was known in English by what name until it was renamed in 1948?
Centigrade
Iridium. Copies in the same 90:10 alloy were sent out to the nations that signed the Metre treaty; the United States received kilograms number 4 and 20.
Q 14Which country's weather forecasts switched from Fahrenheit to Celsius on April Fools' Day 1975?
Canada
Canada. It was the opening move of a metric campaign that put kilometres on the highways two years later, though Canadians still tend to give their own weight in pounds.
Q 15Le Grand K, the metal cylinder that defined the kilogram until 2019, is about the size of what?
Golf ball
Golf ball. Its platinum alloy is almost twice as dense as lead, so a full kilogram of it sits easily in the palm of a hand.
Q 16The 2019 SI revision defines the kilogram by fixing the value of which constant?
The Planck constant
The Planck constant. With its value fixed, a Kibble balance can weigh an object against a precisely measured electromagnetic force, so no master cylinder in a vault is needed.
Q 17The metre's definition fixes which quantity at 299,792,458 metres per second?
The speed of light
The speed of light. Since 1983 a metre has been however far light travels in a vacuum in 1/299,792,458 of a second, so sharper measurements refine the metre rather than light's speed.
Q 18Before 1983, the metre was defined by wavelengths of light from which element?
Krypton-86
Krypton-86. A metre was 1,650,763.73 wavelengths of its orange-red glow, so any well-equipped lab could reproduce the unit without travelling to compare a metal bar.
Q 19The SI launched in 1960 with six base units; which one was added as the seventh in 1971?
Mole
Mole. For decades it was defined through 12 grams of carbon-12, so the chemists' unit quietly depended on the kilogram cylinder locked in a French vault.
Q 20The second has been defined since 1967 by the hyperfine transition frequency of which atom?
Caesium-133
Caesium-133. Louis Essen built the first accurate caesium clock in Britain in 1955, and twelve years later its 9,192,631,770 ticks became the world's second.
Centigrade. The new name honoured Anders Celsius, whose original 1742 thermometer ran the other way, with 0 at boiling and 100 at freezing.
Q 24Which of these electrical units honours a French scientist?
The ampere
The ampere. Defined at an 1881 congress in Paris, it honours André-Marie Ampère, who showed in 1820 that two current-carrying wires attract or repel each other.
Q 25The candela is the SI unit of what?
Luminous intensity
Luminous intensity. The unit's name simply means candle, and an ordinary wax candle still gives off roughly one candela.
Q 26A litre is exactly equal to which volume?
One cubic decimetre
One cubic decimetre. That is a cube just 10 cm on each side; the name comes from the old French litron, itself descended from a Greek word for a pound weight.
Q 27From 1901 to 1964, the litre was defined as the volume of one kilogram of what?
Pure water
Pure water. Careful measurement showed this litre was about 28 parts per million too big, so the water definition was scrapped in 1964.
Q 28Which unit of land area equals a square 100 metres on each side?
The hectare
The hectare. Its name means a hundred ares, the 10-metre squares of France's first metric law, and it works out at about two and a half acres.
Q 29The tonne, or metric ton, corresponds exactly to which SI unit?
The megagram
The megagram. A tonne is a million grams, yet that official name is rarely used; 'tonne' survives from the tun, a huge wine cask that weighed about as much when full.
Q 30Why does the SI rule out a unit like the 'millikilogram'?
Only one prefix per name
Only one prefix per name. The kilogram is the one base unit that already carries a prefix, so its multiples and fractions are built on the gram instead.