The Metric System/ SI-Units (2023)

Metric System/International System of Units (SI)

The metric system is used by scientists, many military units, and all industrialized nations outside the U.S. As a result, this system is important to learn in order to develop your career and travel.


millimeters < centimeters < meters < kilometers

These are the four metric units that are commonly used to measure length. There are many more units that are much shorter than millimeters and much longer than kilometers. Each unit is based on the meter. Its length is some multiple of 10 times the length of a meter.

For example: I kilometer = 1 meterx103

Converting between two metric units just required multiplying by a power of 10.

Here are the most common conversions you'll make in class, on tests, and on trips:

  • 1000 millimeters=1 meter
  • 100 centimeters=1 meter
  • 1000 meters=1 kilometer

As NASA's website explains, all units under a meter use Latin roots. "Milli-" comes from the Latin for 1000, and "centi-" comes from the Latin for 100. These prefixes represent1/1000and1/100of a unit respectively.

Units that are greater than a meter use Greek roots. "Kilo-" comes from the Greek for 1000, and represents 1000 units. There is also a Greek prefix "hecto-" for 100 units, though it's not commonly used.

You can use the table below to practice conversion problems:

The Metric System/ SI-Units (1)

Convert 0.5 meters to centimeters.

1 meter = 100 centimeters

We can set up a proportion to solve:

Cross-multiply to solve for x.

x= 0.5x100

x= 50 centimeters

Convert 0.5 meters to kilometers.

1 kilometer = 1000 meters

We can set up a proportion to solve:

Cross-multiply to solve forx.

1000x= 0.5

x= 0.5/1000

x= 0.0005, or 5x10-4kilometers


4 cm 11 mm + 5 cm 2 mm = ?

To set up this problem, make sure each value is lined up with values that have the same unit.

The Metric System/ SI-Units (2)

Start by adding the values in the right column.

11 mm + 2 mm = 13 mm

Because there are 10 mm in 1 cm, carry a centimeter from the millimeters column into the centimeters column. The 3 mm left over stays in the right column (the process is just like regular arithmetic).

The Metric System/ SI-Units (3)

Now add up the centimeters.

The Metric System/ SI-Units (4)

The sum is10 cm 3 mm.


milligram < grams < kilograms

These prefixes will look familiar, and they have the same meanings:

  • 1000 milligrams=1 gram

  • 1000 grams=1 kilogram

Convert 200 grams to milligrams and kilograms.

To go from grams to milligrams, set up this proportion:

x= 200x1000

x= 200,000 milligrams

Use this proportion to go from grams to kilograms:

1000x= 200

x= 0.2 kilograms

Capacity/Liquid Volume

milliliters < liters
(These are the most commonly used units.)

Liquid Volume

  • 1000 milliliters=1 liter

0.75 liters of water is equal to how many milliliters?

We can set up a proportion to solve:

Cross-multiply to solve.

x= 1000x0.75

x= 750 milliliters

Liquid Volume to Solid Volume

You may also be asked to figure out how many milliliters of water will completely fill a solid container. In this case, you can convert the volume of a solid object to liquid volume. Here are the key conversion rates:

  • 1 cubic millimeter= milliliter

  • 1 cubic meter=1000 liters

If Leigh needs to take 2 liters of water to a training session, what is the minimum volume of the container in which she can carry that water to her session?

We can set up another proportion by using the conversion rate for cubic meters and liters.

1000x= 2

x= 2/1000

x= 0.002 cubic meters

If you memorize the value each prefix represents, you'll be ready to take on measurements like the deciliter, and also understand some other frequently used terms like the kilobyte, megabyte, and gigabyte.


What is the SI unit in the metric system? ›

In the modern form of the International System of Units (SI), the seven base units are: metre for length, kilogram for mass, second for time, ampere for electric current, kelvin for temperature, candela for luminous intensity and mole for amount of substance.

What is the SI system of measurement answers? ›

The International System of Units (SI) is system of units of measurements that is widely used all over the world. This modern form of the Metric system is based around the number 10 for convenience. A set unit of prefixes have been established and are known as the SI prefixes or the metric prefixes (or units).

What are the 7 metric units? ›

Prefixes are provided in scales that function around 7 units known as metric system (or SI) base units. As shown in Table 1, base units include the meter (m), the kilogram (kg), the kelvin (K), the second (s), the ampere (A), the candela (cd), and the mole (mol).

Do the SI system and the metric system use the same units? ›

The SI system of units (often referred to as the metric system) is the official system for measurements in nearly all countries of the world, but not in the U.S.

What is A SI unit example? ›

Unit of length, meter (m): Meter is the SI unit of length and is defined by taking the fixed value of the speed of light in vacuum. It is expressed as m.s-1. Unit of mass, kilogram (kg): Kilogram is the SI unit of mass and is defined by taking the fixed value of the Planck constant. It is expressed as kg.m2.s-1.

Why are SI units? ›

There are several reasons why SI is preferred to the old English system of measurement: SI is not based on the arbitrary construct of the human body; rather, on precise and definite standards. SI uses base 10, just like our number system, so it is much easier to learn, remember and convert between units.

What is the SI system quizlet? ›

SI System. International System of Units, used world wide in science, base of 10. Base unit for length. Meter. Base unit for mass.

What is the meaning of metric measurement? ›

Metric System is basically a system used for measuring distance, length, volume, weight and temperature. It is based on three basic units with which we can measure almost everything in the world. M- meter, used to measure the length. Kg- kilogram, used to measure the mass.

What is the SI unit for volume? ›

Volume is the measure of the 3-dimensional space occupied by matter, or enclosed by a surface, measured in cubic units. The SI unit of volume is the cubic meter (m3), which is a derived unit. Liter (L) is a special name for the cubic decimeter (dm3).

What are the 4 main metric units? ›

In the metric system of measurement, the most common units of distance are millimeters, centimeters, meters, and kilometers.

What are the 3 metric systems? ›

Metric system basics

The three most common base units in the metric system are the meter, gram, and liter.

Why is metric called SI? ›

Also referred to as the metric system, the System of Units is commonly abbreviated as SI, which comes from the original French name, Système international d'unités. The SI standard builds on an earlier system of measurement called the meter-kilogram-second (MKS) system.

Who uses SI units? ›

The seventh base unit, the mole, was added in 1971. SI is now used almost everywhere in the world, except in the United States, Liberia and Myanmar, where the older imperial units are still widely used.

Why do we use the SI metric system? ›

Answer and Explanation: Scientists prefer the International (SI) System of Units, for it is an easier system to use (as opposed to the English System), as many of the SI System's more basic units are given in multiples of ten.

How many basic SI units are there? ›

The SI is founded on seven SI base units for seven base quantities assumed to be mutually independent, as given in Table 1. For detailed information on the SI base units, see Definitions of the SI base units and their Historical context.

What are the two types of SI units? ›

The SI now consists of only two classes of units: base units and derived units.

Is the metric system better? ›

Just looking at the facts, it's easy to argue that the metric system is vastly superior. Nearly every country uses it. This almost universal standard allows you to understand measurements—and be understood—no matter where you are.

How are SI units used in everyday life? ›

In daily life, the Metre measures the length of an object, Mole measures the number of particles in a substance, Second measures the time, Candela measures the luminosity of an object, Kelvin (273K = 00C) measures the temperature of an object, and Ampere measures electrical current.

Which is not an SI unit? ›

The physical units that do not come under SI units are velocity, force, momentum, and magnetic field.

When was the SI system? ›

The International System of Units, universally abbreviated SI (from the French Le Système International d'Unités), is the modern metric system of measurement. The SI was established in 1960 by the 11th General Conference on Weights and Measures (CGPM, Conférence Générale des Poids et Mesures).

Why was the SI system made? ›

The principle behind the International System of Units is to provide the same values for measurements such as length, weight, and time no matter where in the world measurement is performed.

Who found the SI system? ›

The birth of the SI is inseparably linked to Professor Giovanni Giorgi. This visionary Italian anticipated future needs and provided as early as 1901 not only suggestions for a coherent system of units, but also a full-fledged solution.

How did metric system start? ›

The first practical realisation of the metric system came in 1799, during the French Revolution, after the existing system of measures had become impractical for trade, and was replaced by a decimal system based on the kilogram and the metre. The basic units were taken from the natural world.

Who is on the metric system? ›

Today, the metric system, which was created in France, is the official system of measurement for every country in the world except three: the United States, Liberia and Myanmar, also known as Burma. And even then, the metric system is still used for purposes such as global trade.

What is the SI unit for speed? ›

unit of speed is the meter per second (m/s).

What is the SI unit for pressure? ›

The pascal (Pa) is the unit of pressure or stress in the International System of Units (SI). It is named after the scientist and mathematician Blaise Pascal. One pascal is equivalent to 1 newton (N) of force applied over an area of 1 square meter (m2).

What is the SI unit density? ›

Density is defined as the mass per unit volume of a substance. Density = Mass÷Volume. S.I. unit of mass is kg and that of volume is m3. Hence, S.I. unit of density is kg/m3.

What is example of metric? ›

Metric Units

Examples include measuring the thickness or length of a debit card, length of cloth, or distance between two cities. Weight: Gram (g) and Kilogram(kg) are used to measure how heavy an object is, using instruments.

How do you convert SI units? ›

When converting a submultiple unit (smaller quantity) into the SI base unit (larger quantity) divide the submultiple unit by the conversion factor. The millimetre is a submultiple unit (smaller quantity) of the SI base unit of length, the metre. A millimetre is one thousand times smaller than the metre.

What is one metric equal to? ›

1 metric ton = 1000 Kg, and we all know 1 Kg = 1000 gram. So 1 metric ton = 1000(1000) gram = ${10^6}$gram = 1 megagram. So 1 metric ton = 1000 Kg = ${10^6}$gram = 1 megagram.

What is metric system based on? ›

metric system, international decimal system of weights and measures, based on the metre for length and the kilogram for mass, that was adopted in France in 1795 and is now used officially in almost all countries.

How wide is 1m? ›

A meter is a standard metric unit equal to about 3 feet 3 inches. It's 100 times bigger than a centimeter, which is 0.01 meters. A kilometer is 1,000 meters.

Is an ounce a metric unit? ›

The metric system uses units such as meter, liter, and gram to measure length, liquid volume, and mass, just as the U.S. customary system uses feet, quarts, and ounces to measure these.

What is the biggest metric unit? ›

Kilometer (Km)is the largest unit of metric measurement. It is mainly used to measure the length (distance) of various spaces, such as the distance of roads, astronomical distance, etc. Measurement Example: When measuring significant distances, it is easier to use Km than smaller units.

Why does the US not use the metric system? ›

The biggest reasons the U.S. hasn't adopted the metric system are simply time and money. When the Industrial Revolution began in the country, expensive manufacturing plants became a main source of American jobs and consumer products.

What is the first metric? ›

The initial metric unit of mass, the “gram”, was defined as the mass of one cubic centimetre — a cube that is 0.01 metre on each side — of water at its temperature of maximum density. For capacity, the “litre” (spelled “liter” in the US) was defined as the volume of a cubic decimetre — a cube 0.1 metre on each side.

What is SI metric length? ›

What is the SI Unit of Metric Length? In the metric system, the SI unit of length is a meter which is defined as follows: “The metric length of the path that is travelled by light in a vaccum within 1⁄299792458 seconds”.

What is the metric symbol? ›

Units and symbols
Quantity measuredUnitSymbol
Length, width, distance, thickness, girth, etc.millimetremm
Mass (“weight”)*milligrammg
26 more rows
Jan 6, 2023

Does the US use the SI system? ›

U.S. customary units have been defined in terms of metric units since the 19th century, and the SI has been the "preferred system of weights and measures for United States trade and commerce" since 1975 according to United States law.

Why is SI units the best? ›

The greatest advantage of SI is that it has only one unit for each quantity (type of measurement). This means that it is never necessary to convert from one unit to another (within the system) and there are no conversion factors for students to memorize.

What is SI and US units? ›

Conversions Between SI Units and US/English Units
Forcenewton (N)pound (f) or lb (f)
Masskilogram (Kg)pound (m) or lb (m)
Timesecond (sec)second (sec)
Volume (liquid)liter (l)gallon (U.S. gal)
13 more rows

Is Fahrenheit an SI unit? ›

Answer and Explanation: The SI unit of temperature is Kelvin. Fahrenheit and Celsius are also the units of temperature but they do not belong to the International System of units.

Is Kelvin or Celsius SI? ›

The kelvin is the SI unit of thermodynamic temperature, and one of the seven SI base units. Unusually in the SI, we also define another unit of temperature, called the degree Celsius (°C). Temperature in degrees Celsius is obtained by subtracting 273.15 from the numerical value of the temperature expressed in kelvin.

What is SI and imperial units? ›

Imperial units are the old British system now used mostly in the USA. Yards, miles, feet, inches. Pounds, ounces, gallons, etc. Metric units are the SI or MKS system, Meters, liters, kilograms and all the derivatives with prefixes.

Is A Celsius an SI unit? ›

As Celsius is an SI unit derived from Kelvin, it's also linked to ITS-90 and its symbol is the lower case letter t90. In terms of ITS-90, the melting point of the ice is slightly below 0 °C and the boiling point of the water at the normal atmospheric pressure is approximately 99.974 °C.

What is the SI unit of time is hour? ›

Basically time can be measured in seconds or minutes or hours or days. All of these are units of time. But SI units of time are seconds that is the reason most of the constants are measured per unit second or for unit seconds.

What is the unit of time? ›

Hours, minutes, and seconds are units of time. An hour is bigger than a minute, and a minute is bigger than a second. An hour consists of 60 minutes and 1 minute consists of 60 seconds.

What is SI unit of heat? ›

unit of heat is joule (J).

What is the SI unit for electric current? ›

The SI unit of the electric current is ampere (A).

Why doesn't the US use the metric system? ›

The biggest reasons the U.S. hasn't adopted the metric system are simply time and money. When the Industrial Revolution began in the country, expensive manufacturing plants became a main source of American jobs and consumer products.

Who uses metric system? ›

The metric system is the most used measurement system in the world. Only three countries in the world don't use the metric system: the United States, Liberia, and Myanmar. Every other country around the world uses the metric system.


Top Articles
Latest Posts
Article information

Author: Tish Haag

Last Updated: 23/12/2023

Views: 5479

Rating: 4.7 / 5 (47 voted)

Reviews: 94% of readers found this page helpful

Author information

Name: Tish Haag

Birthday: 1999-11-18

Address: 30256 Tara Expressway, Kutchburgh, VT 92892-0078

Phone: +4215847628708

Job: Internal Consulting Engineer

Hobby: Roller skating, Roller skating, Kayaking, Flying, Graffiti, Ghost hunting, scrapbook

Introduction: My name is Tish Haag, I am a excited, delightful, curious, beautiful, agreeable, enchanting, fancy person who loves writing and wants to share my knowledge and understanding with you.