Imperial and Metric Units' Online Conversion

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    Is there any equivalence between Ancient Roman units and the metric system?

    Which were the first countries to use the metric system?
    @unitsconverter



    The metric and imperial systems' main difference

    The main difference between the two systems is that metric units are based on the decimal system while imperial units are based on the British system of measurement. Despite their differences, both systems are used to measure the same physical quantities.

    The metric system, also known as the International System of Units (SI), is used in most countries around the world. It is based on the decimal system, which means that all measurements are based on multiples of 10. For example, the basic unit of length in the metric system is the meter, and it is divided into 100 centimeters and 1,000 millimeters. The basic unit of mass in the metric system is the kilogram, and it is divided into 1,000 grams.

    On the other hand, the imperial system, also known as the British system, is mainly used in the United States, United Kingdom, and other countries that were once part of the British Empire. It is based on the British system of measurement, which means that measurements are based on arbitrary units. For example, the basic unit of length in the imperial system is the yard, which is divided into 3 feet, and the basic unit of mass is the pound, which is divided into 16 ounces.

    The metric and imperial systems have different historical origins

    The metric system has its origins in the French Revolution. In the late 18th century, the French Academy of Sciences proposed a new system of measurement that was based on the decimal system, in which all measurements were based on multiples of 10. This system was designed to be simple and easy to use, and it was intended to replace the existing system of measurement, which was based on arbitrary units and was difficult to use and understand.

    The new system was adopted by the French government in 1795. Over the next century, the metric system was adopted by many other countries, and it eventually became the standard system of measurement in most of the world. It is officially recognized as the international system of units.

    The imperial system has its origins in the British Empire. The system was developed in the 18th century and was based on the British system of measurement, which was used in Great Britain at that time. The basic units of length, mass and volume were derived from the traditional units used in Britain. The imperial system was adopted by the British government in 1824 and was used throughout the British Empire, including the United States, which adopted it in the late 18th century.

    Despite the fact that the imperial system was later replaced in most of the British Empire by the metric system, it is still in use in the United States, United Kingdom, and other countries that were once part of the British Empire.

    The main actors in the creation of the metric system were the French Academy of Sciences and the French government

    The French Academy of Sciences, a group of scientists and scholars, proposed the idea of a new system of measurement based on the decimal system in the late 18th century. The Academy's goal was to create a simple and logical system of measurement that would be easy to use and understand. They believed that a decimal system of measurement would be more rational and efficient than the existing system, which was based on arbitrary units.

    The French government, under the leadership of the National Assembly, was supportive of the Academy's proposal and worked to implement the new system. In 1791, the National Assembly established the Commission of Weights and Measures, which was responsible for developing and promoting the new system. The commission was made up of scientists, including the famous scientist and mathematician, Jean Baptiste Joseph Delambre, and Pierre Méchain, who were appointed to establish the standard for the new system of measurement and conduct the necessary measurements to create the new system.

    The Commission's work was recognized internationally and was the basis for the adoption of the metric system as the International System of Units (SI) which is now the international standard for measurement in most of the world.

    The United States did not fully adopt the metric system for several reasons

    One reason is that the country had already developed a well-established system of measurement based on the British system, which was used in the colonies before the Revolutionary War. This system, known as the "American system," was similar to the imperial system and was based on the yard, pound, and gallon, among other units.

    Another reason is that the metric system was not widely used in the United States during the 19th century, when many other countries were beginning to adopt it. The US had a growing economy and industries that were heavily invested in the existing system of measurement and would have had to bear the cost of converting to the metric system.

    Additionally, there was also a lack of political will to change to the metric system, as many Americans felt that the metric system was foreign and saw no need to change to a system that was not in use in the United States.

    In the late 19th century and the early 20th century, the US government began to realize the benefits of the metric system, such as its simplicity and universality, and started to encourage its use in certain fields such as science, engineering, and education. However, a law mandating the use of the metric system was never passed, and the United States remains one of the few countries in the world that has not officially adopted the metric system as its primary system of measurement.

    Important dates

    1791
    The French National Assembly establishes the Commission of Weights and Measures
    to develop and promote the metric system in France.

    1795
    The French government adopts the metric system as the official system of measurement in France.

    1824
    The British government adopts the imperial system as the official system of measurement in the
    United Kingdom.

    1866
    The United States Congress passes the Metric Act, which allows for the voluntary use of
    the metric system in trade and commerce in the United States.

    1875
    The Treaty of the Meter is signed, establishing the International System of Units (SI)
    based on the metric system, recognized internationally.

    1887
    The United States adopts the International System of Units (SI) as the preferred system of measurement
    for use in scientific work in the United States.

    1960
    The International System of Units (SI) is adopted as the international standard for measurement
    by the General Conference on Weights and Measures (CGPM).

    1975
    The United States Metric Study Act is passed, which establishes a program to promote
    the use of the metric system in the United States.

    1988
    The Omnibus Trade and Competitiveness Act is passed in the United States,
    which makes the metric system the preferred system of measurement for use
    in all federal government agencies in the United States.






    Worldwide use of the Metric System and Date of Metrication

    * The United States of America, Burma and Liberia have not yet adopted the Metric System (SI).

    Metrication per country

    Conversion Table
    U.S. unit Metric equivalent
    Metric unit U.S. equivalent
     

    Inch (in)

    Centimeter (cm)

    2.54 centimeters

    0.394 inch

    Foot (ft)

    Meter (m)

    0.305 meter

    3.28 feet

    Yard (yd)

    Meter (m)

    0.914 meter

    1.09 yard

    Mile (mi)

    Kilometer (km)

    1.61 kilometer

    0.621 mile

    Square inch (in2)

    Square centimeter (cm2)

    6.45 square centimeters (cm2)

    0.155 square inch (in2)

    Square foot (ft2)

    Square meter (m2)

    0.093 square meter (m2)

    10.8 square feet (ft2)

    Square yard (yd2)

    Square meter (m2)

    0.836 square meter (m2)

    1.2 square yard (yd2)

    Square mile (mi2)

    Square kilometer (km2)

    2.56 square kilometers (km2)

    0.386 square mile (mi2)

    Acre

    Hectare (ha)

    0.405 hectare

    2.47 acres

    Cubic foot (ft3)

    Cubic meter (m3)

    0.028 cubic meter (m3)

    35.28 cubic feet (ft3)

    Quart (qt)

    Liter (l)

    0.946 liter

    1.06 quart

    Gallon

    Cubic inch (in3)

    231 cubic inches (in3)

    0.0043 gallon

    Ounce (oz)

    Gram (g)

    28.3 grams

    0.035 ounce

    Pound (lb)

    Kilogram (kg)

    0.454 kilogram

    2.2 pounds



    Units per conversion type
    Area
    • square meter (m2)
    • are (a) = 100 sq. meters (m2)
    • hectare (ha) = 100 Ares = 10 000 sq. meters
    • square kilometer (km2) = 100 hectares = 10000 Ares = 1 000 000 sq. meters
    • square mega meter (Mm2) = 1 000 000 000 000 sq. meters
    • square foot = 144 sq. inches = 0.09290304 sq. meters
    • square yard = 9 sq. feet = 0.83612736 sq. meters
    • square perch = 30.25 sq. yards = 25.2928526 sq. meters
    • acre = 10 sq. chains = one furlong by one chain = 160 sq. perches = 4840 sq. yards = 43 560 sq. feet = 4046.8564224 sq. meters
    • square mile = 640 acres = 2.589988110336 sq. kilometers

    Metric System Imperial
    1 square centimeter [cm2] 100 square millimeters 0.001076391 square feet
    1 square meter [m2] 10000 square centimeters 1.19599004630 square yard
    1 hectare [ha] 10000 square meters 2.47105381467 acres
    1 square kilometer [km2] 100 hectares 0.38610215854 square mile

    Imperial Metric System
    1 square inch [in2] 6.4516 square centimeters
    1 square foot [ft2] 144 square inches 0.09290303999 square meter
    1 square yard [yd2] 9 square feet 0.83612736 square meter
    1 acre 4840 square yards 4046.8564224 square meters
    1 square mile 640 acres 2.589988110336 square kilometers


    Length

    Main length units:
    • meter
    • centimeter
    • kilometer
    • inch
    • foot
    • yard
    • mile
    • light-year (astronomical unit)
    • parsec (astronomical unit)
    • angstrom (microscopic unit)

    Metric System Imperial
    1 millimeter [mm] 0.03937007874 inch
    1 centimeter [cm] 10 millimeters 0.3937007874 inch
    1 meter [m] 100 centimeters 1.09361329833 yard
    1 kilometer [km] 1000 meters 0.62137119223 mile

    Imperial Metric System
    1 inch [in] 2.54 centimeters
    1 foot [ft] 12 inches 0.3048 meter
    1 yard [yd] 3 feet 0.9144 meter
    1 mile 1760 yards 1.609344 kilometer


    Weight and Mass

    Main weight units:
    • gram (g) = 11000 kg
    • kilogram (kg)
    • tonne (t)= 1 000 kg
    • electronvolt (eV)
    • atomic mass unit (u)
    • slug (sl)
    • pound (lb)
    • Planck mass (mP)
    • solar mass (M)
    • Compton wavelength
    • Schwarzschild radius

    Metric System Imperial
    1 milligram [mg] 0.01543209876 grain
    1 gram [g] 1000 milligrams 0.03527399072 ounce
    1 kilogram [kg] 1000 grams 2.20458553791 pounds
    1 tonne [t] 1000 kilograms 0.98418997228 ton

    Imperial Metric System
    1 ounce [oz] 437.4922839506173 grains 28.3495 grams
    1 pound [lb] 16 ounces 0.4536 kilogram
    1 stone 14 pounds 6.35 kilograms
    1 hundredweight [cwt] 112 pounds 50.8032 kilograms
    1 ton 20 hundredweights 1.016064 tonne


    Volume

    Main volume units:
    • cubic inch (cu in) or (in3)
    • cubic foot (cu ft) or (ft3)
    • cubic yard (cu yd) or (yd3)
    • acre foot (acre ft)
    • minim (min)
    • US fluid dram (fl dr)
    • teaspoon (tsp)
    • tablespoon (Tbsp)
    • US fluid ounce (fl oz)
    • jigger (jig)
    • US gill (gi)
    • US cup (cp)
    • US pint (pt)
    • US quart (qt)
    • US gallon (gal)
    • barrel (bbl)
    • hogshead
    • pint (pt)
    • quart (qt)
    • gallon (gal)
    • peck (pk)
    • bushel (bu)
    • fluid ounce (fl oz)
    • gill

    Metric System Imperial
    1 cubic centimeter [cm3] 0.06102361003 cubic inch
    1 cubic decimeter [dm3] 1000 cubic centimeters 0.03531458914 cubic foot
    1 cubic meter [m3] 1000 cubic decimeters 1.30794774594 cubic yard
    1 liter [l] 1 cubic decimeter 1.75975011548 pint
    1 hectoliter [hl] 100 liters 21.9968764435 gallons

    Imperial Metric System
    1 cubic inch [in3] 16.3871 cubic centimeters
    1 cubic foot [ft3] 1728 cubic inch 0.0283169088 cubic meter
    1 fluid ounce [fl oz] 28.413125 milliliters
    1 pint [pt] 20 fluid ounces 0.5682625 liter
    1 gallon [gal] 8 pints 4.5461 liters


    Energy

    Main energy units:
    • ergs
    • calories
    • joule
    • kilowatt hour = 3.6 million joules
    • British thermal unit (BTU) = 1055 joules (approx.)


    Flow rate

    Definition: volume of fluid passing through a particular surface per unit time (i.e.: cubic meters per minute or cubic feet per minute).

    Symbol: Q.

    Also know as:

    • volumetric flow rate
    • volume flow rate
    • rate of fluid flow


    Force

    Force units:
    • Newton
    • dyne
    • kilogram-force
    • pound-force
    • poundal


    Power

    Main power units:
    • watt (W) = 1 joule per second
    • ergs per second (erg/s)
    • horsepower (hp) = 33 000 foot-pounds per minute = 746 watts
    • metric horsepower [Pferdestärke (PS) or cheval vapeur (CV)]
    • foot-pounds per minute
    • dBm
    • calories per hour
    • kilocalories per hour
    • Btu per hour (Btu/h)
    • tons of refrigeration = 12 000 Btu/h


    Pressure

    Main pressure units:
    • Pascal (Pa) = one Newton per square meter
    • pound per square inch (psi)
    • bar
    • barye (ba) = dyne per square centimeter
    • hectoPascal (hPa)
    • kiloPascal (kPa)
    • millibar (mbar)
    • inch of mercury (inHg)
    • decibar (dbar) = increase of 1 meter (depth)
    • rule of thumb (for scuba divers)
    • standard atmosphere (atm) = 101 325 Pa = 101.325 kPa = 1013.25 hPa
    • millimeters of mercury (mmHg) = one torr
    • inches of mercury
    • millimeter, centimeter, meter, inch and foot of water
    • kip, ton-force (short), ton-force (long), pound-force, ounce-force and poundal per square inch
    • kg-force, or kilopond, per square cm
    • gram-force and tonne-force (metric ton-force per square cm
    • kg-force and tonne-force per square meter
    • sthene per square meter (pieze)


    Temperature

    Main temperature units:
    • Kelvin (K)
    • Celsius
    • Fahrenheit
    • electronvolts (eV)= 11 605 K
    • kiloelectronvolts (keV)
    • Rankine


    Velocity

    Main velocity units:
    • Meters per second (m s−1 or m/s)
    • Kilometers per hour (km/h)
    • Miles per hour (mph)
    • Knots (nautical miles per hour [kn or kt])
    • Feet per second (fps or ft/s)
    • Mach number = speed divided by the speed of sound
    • Speed of light in vacuum (c = 299 792 458 m/s)




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