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:


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.


1 meterA meter is equal to 100 centimeters.

1 meter = 100 centimeters


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


roadsA kilometer is equal to 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

Activity: Discover Lengths