# Units of Length - Maths with Mum (2023)

## Metric Units of Length

From smallest to largest, the metric units of length are millimetres (mm), centimetres (cm), metres (m) and kilometres (km). There are 10 mm in 1 cm, 100 cm in 1 m and 1000 m in 1 km. The metric units of length are used in all countries except the USA, Liberia and Myanmar.

Here is a table showing the most common metric units of length and how to convert between them.

To convert between metric units of length, use the following rules:

• To convert cm to mm, multiply by 10.
• To convert m to cm, multiply by 100.
• To convert km to m, multiply by 1000.
• To convert mm to cm, divide by 10.
• To convert cm to m, divide by 100.
• To convert m to km, divide by 1000.

Here are some examples of converting between metric units:

Original Metric UnitConversionEquivalent Metric Unit
20 mm÷ 102 cm
36 mm÷ 103.6 cm
200 cm÷ 1002 m
518 cm÷ 1005.18 m
5000 m÷ 10005 km
7200 m÷ 10007.2 km
8 km× 10008000 m
6.3 km× 10006300 m
5 m× 100500 cm
3.4 m× 100340 cm
9 cm× 1090 mm
6.5 cm× 1065 cm
3 km× 100 000300 000 cm
2.5 m× 10002500 mm

## Imperial Units of Length

From smallest to largest, the most common imperial units of length are inches (in), yards (yd), feet (ft) and miles (mi). There are 12 inches in a foot, 3 feet in a yard and 1760 yards in a mile. Imperial units of length are used in the USA, Liberia and Myanmar.

Here is a table showing the most common imperial units of length and how to convert between them.

(Video) Metric Units of Length | Convert mm, cm, m and km

To convert between metric units of length, use the following rules:

• To convert feet to inches, multiply by 12.
• To convert yards to feet, multiply by 3.
• To convert miles to yards, multiply by 1760.
• To convert inches to feet, divide by 12.
• To convert feet to yards, divide by 3.
• To convert yards to miles, divide by 1760.

## What is the Difference Between Metric and Imperial Units?

Metric units use base 10 conversions, whereas imperial units do not. This means that it is easier to convert between metric units by multiplying or dividing by 10, 100 or 1000.

Metric units have a consistent conversion ratio across different measurements whereas imperial units do not. This makes it easier to remember and work with metric units. For example, to convert from kilometres to metres, we multiply by 1000 and to convert from kilograms to grams, we also multiply by 1000. We do not have similar patterns with imperial units such as inches to feet or ounces to pounds, which can make it more challenging to work with these units.

Metric units are used consistently in most countries throughout the world. Only America, Libera and Myanmar officially use imperial units. These countries still use these traditional imperial units because they have been working with imperial units for many years and it would be costly to convert everything into metric units.

Although similar in size, a metre is not the same length as a yard. 1 m is equal to 1.09 yards and so, 1 metre is longer than 1 yard by approximately 3 inches or 8 centimetres.

A centimetre is smaller than an inch. A centimetre is less than half the size of an inch. 1 inch is approximately equal to 2.5 centimetres.

## Units of Length List

The most common units for length are shown in the list below with examples:

Metric Units of LengthExampleConversion
1 millimetre (mm)Thickness of a staple10 mm = 1 cm
1 centimetre (cm)The width of a little finger100 cm = 1 m
1 metre (m)The width of a doorway1000 m = 1 km
1 kilometre (km)Roads are measured in kilometres1000 m = 1 km
Imperial Units of LengthExampleConversion
1 inchThe size of television screens12 inches = 1 foot
1 footPeople’s height3 feet = 1 yard
1 yardThe size of rooms or buildings1760 yards = 1 mile
1 mileThe distance between cities1760 yards = 1 mile

Other less commonly used units of length are nanometres and micrometres. These units of length are used to measure incredibly small distances as seen under a microscope.

(Video) Common metric units of length: kilometers, meters, centimeters & millimeters (3rd grade math)

In imperial units, 1 thou is one thousandth of 1 inch. 1000 thous make up 1 inch.

3 miles is called 1 league.

## How to Choose an Appropriate Unit of Length

From smallest to largest, the common units of length are millimetres, centimetres, metres and kilometres.

Millimetres are typically used to measure very small objects, such as objects you can hold in your closed hand. Centimetres are typically used to measure objects that are shorter than the width of a door. Metres are typically used to measure objects that are longer than the width of a door. Kilometres are used to measure the distances between towns, cities or countries.

Here is an example of measuring a seed in millimetres. The seed is 8 mm long and it is less than 1 cm. We know that millimeters would be an appropriate choice of unit to measure this seed because the seed is not even 1 centimetre long.

It is always possible to use a smaller unit of measurement than is typically used. This may be done to measure something to a greater degree of accuracy.

For example, a phone screen is large enough to be measured in centimetres but its size might be given in millimetres for a greater level of accuracy.

(Video) How to Measure Different Objects in Centimetres using a Ruler!

Here is an example of measuring a pencil in centimetres. The pencil is 12 cm long. If an object can be measured well with a ruler, centimetres are a good choice of unit.

It is easier to say 12 cm than 120 mm. The next unit up after centimetres is metres and this pencil is not even 1 metre long.

Metres are a typical unit of length chosen to measure the size of buildings. Below is an example of measuring the size of a house in metres. Distances between towns, cities and countries are always measured in kilometres.

For example, the distance between the two cities of London and Manchester is approximately 300 km. (Video) The Maths Mum® explains ADDITION & SUBTRACTION - PART 1

Here are some examples of selecting the most appropriate unit of measurement:

ObjectMost appropriate unit of measurementActual measurement
The length of a grain of riceMillimetres7 mm
A blueberryMillimetres12 mm
An eraserMillimetres or centimetres45 mm or 4.5 cm
An appleCentimetres10 cm
An A4 pageCentimetres29.7 cm
A manCentimetres or metres180 cm or 1.8 m
A busMetres12 m
The height of a skyscraperMetres150 m
The distance between the UK and the USAKilometres7000 km

## Examples of Objects 1 mm Long

A millimetre is the smallest measurement that can be made using a ruler.

The size of a millimetre is shown below. Some examples of objects 1 mm long are:

• The width of a staple
• The width of a sharp pencil tip
• The thickness of a piece of card
• The thickness of a bank card
• The width of a poppy seed

## Examples of Objects 1 cm Long

A centimetre is about the width of a little finger. It is the distance between the large numbers on a ruler. Some examples of objects 1 cm long are:

• The width of your little finger
• The length of a staple
• The width of a pea
• The length of a coffee bean

## Examples of Objects 1 m Long

Some examples of objects 1 m long are:

(Video) Understanding mm, cm, m, and km

• The length of a baseball bat
• The length of a staple
• The height of a door handle from the ground
• The height of a person’s hips from the ground
• The lengths of a guitar
• The largest footstep you can make

A metre is about as tall as a small child. However a fully grown adult may be just below 2 metres tall. ## Examples of Things that are 1 km Long

Some examples of things that are 1 km long are:

• The Golden Gate Bridge
• The distance walked in 15 minutes
• The world’s tallest skyscrapers

## FAQs

### What are the 7 units of length? ›

The metric system includes kilometer, hectometer, decameter, meter, decimeter, centimeter, and millimeter.

What are the 5 units of length? ›

The basic units for length or distance measurements in the English system are the inch, foot, yard, and mile. Other units of length also include the rod, furlong, and chain.

What are the units of measuring length? ›

In the metric system, length or distance is expressed in terms of kilometers (km), meters (m), decimeter (dm), centimeters (cm), millimeters (mm). It is possible to convert units from km to m or from m to cm or from cm to mm and so on.

What is the basic unit of length and mass? ›

The meter, symbol m, is the SI unit of length. It is defined by taking the fixed numerical value of the speed of light in vacuum c to be 299 792 458 when expressed in the unit m s-1, where the second is defined in terms of ΔνCs. The kilogram, symbol kg, is the SI unit of mass.

What are 10 units of measurement? ›

Share
• Length - meter (m)
• Time - second (s)
• Amount of substance - mole (mole)
• Electric current - ampere (A)
• Temperature - kelvin (K)
• Luminous intensity - candela (cd)
• Mass - kilogram (kg)
Apr 12, 2010

What is length example in math? ›

Length is defined as the measurement or extent of something from end to end. In other words, it is the larger of the two or the highest of three dimensions of geometrical shapes or objects. For example, a rectangle has its dimensions as length and breadth.

How do you write units of length? ›

1. Sentences and measurements. NEVER begin any sentence with digits or symbols or units. ...
2. Space between digit and unit. When writing a measured unit, the numerical value comes first, followed by a space, followed by the unit. ...
4. foot or feet. ...
5. gallon. ...
6. inches. ...
7. kelvin. ...
8. kiloohm, kilohm, kilo-ohm, kilo ohm.

What is a unit in math? ›

In math, the word unit can be defined as the rightmost position in a number or the one's place. Here, 3 is the unit's number in the number 6713. A unit may also mean the standard units used for measurement.

What is the symbol for length? ›

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

What are the 3 types of measurement? ›

You can see there are four different types of measurement scales (nominal, ordinal, interval and ratio).

### What are standard units? ›

A standard unit is a globally accepted unit of measurement. It is accurate everywhere in the world. It is convenient to use by everyone, everywhere. The SI unit of length, metre(m), is a standard unit.

Is mass a unit length? ›

The linear mass density,i.e., mass per unit length L is given by ρ=ρ0(1+xl), where ρ0 is constant, x is distance from the left end.

What is the first unit of length? ›

The Egyptian cubit, the Indus Valley units of length referred to above and the Mesopotamian cubit were used in the 3rd millennium BC and are the earliest known units used by ancient peoples to measure length.

What is mass in length? ›

What is Mass per Unit Length? The mass per unit length is the linear density of a one-dimensional substance such as a wire or thread. Its practical application is in measuring the weight of threads and yarns in the textile industry.

What are the units of length in order from smallest to largest? ›

From smallest to largest, the metric units of length are millimetres (mm), centimetres (cm), metres (m) and kilometres (km). There are 10 mm in 1 cm, 100 cm in 1 m and 1000 m in 1 km. The metric units of length are used in all countries except the USA, Liberia and Myanmar.

What are small units of length? ›

To measure length, there are different units. The bigger unit of measuring length is known to be kilometres. On the other hand, to measure smaller units of length, we use decimeters, centimetres, and millimetres. The standard unit of length is “metre”, which is written as 'm'.

How do you measure length in math? ›

Measuring length means measurement of the length of any object with the help of measuring tools like a ruler, measuring tape, etc. For example, the length of a pencil can be measured in inches using a ruler. The height of students in a class can be measured using a feet scale.

How do you find length in math? ›

If you have the area A and width w , its length w is determined as h = A/w . If you have the perimeter P and width w , its length can be found with h = P/2−w . If you have the diagonal d and width w , it's length is h = √(d²−w²) .

How do you write units and numbers? ›

Spell out numbers one through nine, except in the case of units of measure or time. For these, and for values of 10 and higher, use Arabic numerals. Always spell out numbers at the beginning of a sentence if the sentence cannot be rearranged to avoid starting with a number.

How do you write a unit in math? ›

We usually write units just using their abbrevations.
1. Example: km for kilometer.
2. Example: m/s (or m s-1) for meter per second. m/s is a unit of speed.
3. Example: kg/m3 (or kg m-3) for kilogram per cubic meter. kg/m3 is a unit of density: how much mass per unit of volume.

### How do you find a unit? ›

How to Find Unit Rate? In a unit rate, the denominator is always 1. So, to find unit rate, divide the denominator with the numerator in a way that the denominator becomes 1. For example, if 50km is covered in 5.5 hours, the unit rate will be 50km/5.5 hours = 9.09 km/hour.

What are types of unit? ›

Types of units of measurement list
• CGS system units.
• FPS system units.
• MKS system units.
• SI units.

What are the symbols for units? ›

The SI unit symbols are typically shortened versions of the unit name. For example, the base units of seconds, meters, kilograms, amperes, kelvins, moles and candelas have the unit symbols of s, m, kg, A, K, mol and cd. The unit names may be extended by attaching a prefix, indicating a power of ten.

What is the base unit and symbol for length? ›

meter m

What are old units of length? ›

The standard linear measure in the Imperial system was the mile, which was divided into furlongs, chains, yards, feet and inches. The mile was based on a Roman measurement of 1,000 paces. The word 'furlong' comes from 'a furrow long', or the distance that could be ploughed by an ox without a rest.

What are the 4 common types of measurement? ›

Psychologist Stanley Stevens developed the four common scales of measurement: nominal, ordinal, interval and ratio. Each scale of measurement has properties that determine how to properly analyse the data. The properties evaluated are identity, magnitude, equal intervals and a minimum value of zero.

What are the 3 most common units of measurement? ›

For example, the distance of a road is how long the road is. In the metric system of measurement, the most common units of distance are millimeters, centimeters, meters, and kilometers.

What are the 4 scales of measurement? ›

The four scales of measurement are nominal, ordinal, interval, and ratio. Nominal: Categorical data and numbers that are simply used as identifiers or names represent a nominal scale of measurement.

Why are standard units in measurement? ›

There are mainly two important purposes of using standard units, they are: To measure the quantities accurately. To convey the measurements to other people so that they understand those measurements accurately and follow the same further.

What are the 2 types of measurement? ›

This page explains the two most common systems of measurement: the metric system, used widely in Europe and most of the rest of the world, and the Imperial or British system, a form of which is now chiefly used in the USA.

### What are the 7 standard base units? ›

The present SI has seven base quantities: time, length, mass, electric current, thermodynamic temperature, amount of substance, and luminous intensity.

What are the 7 base dimensions? ›

In total, there are seven primary dimensions. Primary (sometimes called basic) dimensions are defined as independent or fundamental dimensions, from which other dimensions can be obtained. The primary dimensions are: mass, length, time, temperature, electric current, amount of light, and amount of matter.

What are the seven 7 units of measure for the metric system? ›

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).

How many different units of length are there? ›

From smallest to largest, the metric units of length are millimetres (mm), centimetres (cm), metres (m) and kilometres (km). There are 10 mm in 1 cm, 100 cm in 1 m and 1000 m in 1 km. The metric units of length are used in all countries except the USA, Liberia and Myanmar.

How many units are there? ›

There are seven fundamental units in the SI system of units which are mass, length, time, temperature, electric current, mole and luminous intensity.

How do they list dimensions? ›

All box dimensions are written as length x width x height. For example, 14" x 11" x 4" means 14" (L) x 11" (W) x 4" (H)". Please let us know if your box dimensions are inner or outer box dimensions.

What are the 7 base units and what does each measure? ›

The units and their physical quantities are the second for time, the metre (sometimes spelled meter) for length or distance, the kilogram for mass, the ampere for electric current, the kelvin for thermodynamic temperature, the mole for amount of substance, and the candela for luminous intensity.

What are the 3 dimensions in order? ›

Measurement: Length, width, height, depth.

What are the 4 most common metric units of length? ›

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

What are 5 standard metric units? ›

Metric Units

Length: Millimeter (mm), Decimeter (dm), Centimeter (cm), Meter (m), and Kilometer (km) are used to measure how long or wide or tall an object is.

### What are the basic metric units? ›

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 are 3 types of units? ›

The three fundamental units are:
• Mass: Mass is the measure of the amount of matter in a body. The fundamental unit of mass is Kilogram .
• Time: Time is a measurable period. The basic fundamental unit of time is second .
• Length: The length of an object is the distance between the two ends of an object.

What are 4 units? ›

Four Unit Dwelling means a Building arranged or designed to have only four Dwelling Units under one ownership on one Lot, such as a fourplex.

How do you calculate units? ›

Take the total value of the items and divide it by the number of items within the group to determine the unit value for each.

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