image of rulerThe metre is the standard of length, which is divided into 100 centimetres,
also into 1000 millimetres. 1000 metres is the same as 1 kilometre.
And we can also see that 10 millimetres is the same as 1 centimetre.

These distances can all be abbreviated to 1 or 2 letters for ease of use, especially in writing. A table of these measures is shown below:

Length Symbol Relationship to metre Typical item of approx size, etc.
metre m 1 Height of door handle in the home
centimetre cm 1 m = 100 cm Diameter of shirt button
millimetre mm 1 m = 1 000 mm Thickness of a compact disc;
thickness of a UK 5 pence coin
(aka micron)
µm 1 m = 1 000 000 µm Size of hole in vacuum filter; diameter of human hair can range from 17 to 181 µm
kilometre km 1 000 m = 1 km Central span of the Forth road bridge

Height is the same as length, but measured vertically. Heights can be measured in centimetres, metres and kilometres. And from length we get speed, which is length per unit time, e.g. kilometres per hour. Click here for speed info page.

Here are some examples of items and their lengths/heights shown in metric units; at least some of these things you have probably encountered, the metric dimensions will help provide a feel for such sizes as 90 mm or 100 metres:

Floppy disk: 90 mm / 9 cm
Compact disc: 120 mm
Credit card: 85.5 × 54 × 0.8 mm
Matchstick: 2 mm wide
Football pitch (soccer): 100 metres long

Every full-sized soccer pitch must be between 91-119 metres long, and between 46-91 metres wide.

Computer monitor has viewable screen size of 41 cm on average
Average computer monitor, viewable screen size measured diagonally, on CRT monitor: 41 cm

(Tube size is larger)

Eiffel Tower in Paris is 300 metres high
Height of the Eiffel Tower: 300 metres
Great Pyramid of Giza is 147 metres high
Original height of the Great Pyramid of Giza: 147 metres
Empire State Building in New York is 448 metres high
Height of the Empire State Building: 448 metres
Height of average British man: 176 centimetres
Height of average British woman: 162 centimetres
Newborn baby is about 50 centimetres long on average
Average length of new born baby: 50 centimetres
London bus
London double-decker routemaster bus: approx 8.4 metres long, 4.4 metres high, 2.4 metres wide.

Modern London buses vary considerably in length, height and design.

United Kingdom coins

UK pound coin

£1 coin

Diameter: 23.03-23.43 mm
Thickness: 2.8 mm
Mass: 8.75 g

Uk 2 pound coin

£2 coin

Diameter: 28.4 mm
Thickness: 2.50 mm
Mass: 12 g

UK 50 pence coin

50 pence coin

Diameter: 27.3 mm
Thickness: 1.78 mm
Mass: 8.0 g

UK 20 pence coin

20 pence coin

Diameter: 21.4 mm
Thickness: 1.7 mm
Mass: 5.0 g

UK 10 pence coin

10 pence coin

Diameter: 24.5 mm
Thickness: 1.78 mm
Mass: 6.5 g

5 pence coin

Diameter: 18.0 mm
Thickness: 1.0 mm
Mass: 3.25 g

(coin images and data from the Royal Mint website)

If you are interested in the smaller sizes, have a look at the interactive animation at http://www.cellsalive.com/howbig.htm which will even show you nanometres.


Distances between cities, for runs, marathons, and longer distances can be measured using kilometres. As we see above, one kilometre is 1000 metres in length.

Some distances in kilometres:

Location from/to Distance Notes
Earth has circumference of approx 40 thousand kmCircumference of the Earth through the poles 40 000 km This is what the metre was originally based on, but due to slight inaccuracies the exact distance is slightly different (actual length varies according to which website you look at).
Circumference of the Earth around the Equator 40 075 km Distance around the Equator is slightly more due to the bulging of the Earth
Length of Great Britain 1000 km One tenth of the distance from the North Pole to the Equator
Length of coastland of Great Britain (mainland only) 17 819 km

National Grid squares

100 km by 100 km Ordnance Survey in the UK produces all the official maps of the country, and divides the country into 91 grid squares, each with two letters, and covering a distance of 100 km on each side of the square. Using this grid and its subdivisions, any place in the UK can be described using its grid reference. More info.

The grid is divided smaller into 10 km and 1 km grid squares. The OS has been using this metric grid since the mid 1940s.

Astronomical Unit 149 000 000 km The average distance between the Earth and the Sun, 149 million kilometres.
Light Year 9 460 000 000 000 km The distance travelled by light in one year, 9 trillion 460 billion kilometres.
Minimum height of a mountain in England, Wales, Ireland 610 metres This is the definition of what constitutes a mountain. If it is smaller than this height, it is not a mountain. Scotland has different classifications.
Typical altitude of airliner 11 km
The edge of space 100 km The Ansari X Prize was won by SpaceShip One when it reached the edge of space twice.
Distance to the Moon From 356 371 km to 406 720 km The Moon’s orbit is elliptical so the distance varies


42.195 km The official marathon length, however some running races called marathons may be different distances, such as 40 km, 50 km, and is estimated to have been originally 34.5 km in ancient Greece.
UK distances Measured as a straight line, not road distances Road distance using most likely route
London-Manchester 263 km 325 km
London-Edinburgh 534 km 663 km
London-York 280 km 340 km
London-Newcastle 398 km 459 km
Manchester-Edinburgh 281 km 359 km
Total length of motorways in Great Britain 4353 km
Total length of A roads in Great Britain 48 164 km
Total length of B roads in Great Britain 30 216 km