How long is a millimeter


You surely know lengths from your daily life in many areas, such as your height in cm (= centimeters).

You can measure lengths. Measuring devices are, for example, a set square, a ruler, a folding rule or a tape measure.

Images: (Jonathan Werner); Druwe & Polastri; (rusm);
Michael Fabian

You probably remember that:

  • 1 cm = 10 mm
  • 1 m = 100 cm
  • 1 km = 1000 m
  • “Centi” means hundredths, so a centimeter is the hundredth of a meter.
  • “Kilo” means 1000, so one kilometer is 1000 meters.
  • "Milli" means thousandths.

Examples of lengths

1 mm: thickness of your set square
5 mm: width of a box in your math notebook

1 cm: Approximate width of a fingernail
4 cm: diameter of a tea light

Image: Panther Media GmbH (Kitch Bain)

10 cm: width of toilet paper
21 cm: width of your notebooks
50 cm: width of a refrigerator

Image: Druwe & Polastri

1 m: height of the green area of ​​blackboards
2 m: height of doors
2.13 m: height of basketball star Dirk Nowitzki

Image: Picture-Alliance GmbH (Sven Simon)

9 m: approximate length of a classroom
60 m: width of a sports field
100 m: length of a soccer field

Image: Andreas Fanroth

828 m: Burj Khalifa (Dubai), the tallest building in the world

Image: (dblight)

There are also other length measures, especially in English-speaking countries. There is yard, feet, nautical mile, cubit, spoke, mile, ... but you don't need them.

Further in kilometers

1 km: You can walk in about 10 minutes
10 km: You can go 100 km / h in a car in 6 minutes
100 km: Of course you can do 100 km / h in one hour
1000 km: Approximate length from Germany, i.e. from Bavaria in the south to Schleswig-Holstein in the north

Image: (moonrun)

40,000 km: Once around the equator of the earth

Image: Markus Berger

384,000 km: once to the moon
149,000,000 km: Once to the sun

Image: NASA

700,000,000,000,000,000,000,000 km: the width of our universe, that's 23 zeros, the number is already very large!

Image: NASA

In astronomy, that is, celestial science, there is still the light year. That is the distance that light travels in one year, that is an unbelievable 9,400,000,000,000 km.

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Estimating lengths

How far is the route approximately? How high is the room? Sometimes you need an approximate length quickly. Then you guess the lengths.

Estimate means you are giving the approximate length of something.

To do this, you compare what you are looking for with a length that you know.

Example: the foot monument for Uwe Seeler in Hamburg. “Our Uwe” was one of the greatest German footballers of all time.

How high is the monument roughly?

Image: Picture-Alliance GmbH (dpa)

If you know some of your body lengths, you have many estimates under control:

  • Length of your little finger
  • Width of your middle finger
  • Distance from the elbow to the tip of your middle finger
  • Your height

Solution of the estimation problem

The average man is about six feet tall.
Stack the Uwe on top of each other: The foot is about the size of 2 Uwe's.
So 1.80 + 1.80 = 3.60 m.

The foot monument is about 3.60 m high.

Image: Picture-Alliance GmbH (dpa)

Compare a length that you should estimate with lengths that you roughly know:

  • Adults are about 1.80 m tall on average, younger ones a little less.
  • Ordinary cars (not these big ones) are about 4 m long and 1.50 m high.
  • A worksheet from school (= A4) is 21 cm wide and 29.7 cm high.