Metric Length

We can measure how long things are, or how tall, or how far apart they are. Those are are all examples of length measurements.

20cm fork
Example: This fork is 20 centimeters long

These are the most common measurements:

  • Millimeters
  • Centimeters
  • Meters
  • Kilometers


id card

Small units of length are called millimeters.

A millimeter is about the thickness of a plastic id card (or credit card).

Or about the thickness of 10 sheets of paper on top of each other.

This is a very small measurement!



When we have 10 millimeters, it can be called a centimeter.

1 centimeter = 10 millimeters

A fingernail is about one centimeter wide.

tape measures mm and cm side-by-side
Two tape measures, one in mm, the other in cm

We can use millimeters or centimeters to measure how tall we are, or how wide a table is, but to measure the length of a football field it is better to use meters.


A meter is equal to 100 centimeters.

1 meter = 100 centimeters

1 meter
The length of this guitar is about 1 meter

Meters can be used to measure the length of a house, or the size of a playground.

And because a centimeter is 10 millimeters:

1 meter = 1000 millimeters

dog next to chair: 1m = 100cm = 1000mm
The back of this kitchen chair is 1 meter



A kilometer is equal to 1000 meters.

1 kilometer = 1000 meters

When we need to get from one place to another, we measure the distance using kilometers.

The distance from one city to another or how far a plane travels can be measured using kilometers.


In Summary:

mm x10 cm x100 m x1000 km

10 millimeters = 1 centimeter

100 centimeters = 1 meter

1000 meters = 1 kilometer

Lots of Examples

A centimeter (cm) is about:

A meter (m) is about:

man step One meter is about one long step of an adult man.


A kilometer (km) is about:

walking   One kilometer is around a 12 minute walk.


length continuum   Also see
Lengths From Very Small
to Very Large


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