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 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.


Final thoughts about measuring length:

mm x10 cm x100 m x1000 km

1 centimeter = 10 millimeters

1 meter = 100 centimeters

1 kilometer = 1000 meters

Lots of Examples

A centimeter (cm) is about:

  • about as long as a staple
  • the width of a highlighter
  • the diameter of a belly button
  • the width of 5 CD's stacked on top of each other
  • the thickness of a notepad.
  • the radius (half the diameter) of a US penny

A meter (m) is about:

  • a little more than a yard (1 yard is exactly 0.9144 meters)
  • the width of a doorway (most doorways are about 0.8 to 0.9 m)
  • half the length of a bed
  • the width of a large fridge
  • the height of a countertop
  • four rungs up a ladder
  • five steps up a staircase
  • the depth of the shallow end of a swimming pool
  • the width of a dining table
  • the height of a 5 year old
  • shoulder to opposite wrist of an adult
  • outstreched arms of a child
  • waist high on an adult
man step One meter equals roughly one long step of an adult man.


A kilometer (km) is about:

  • a little over half a mile
  • a quarter of the average depth of the ocean
walking   One kilometer equals about 12 minutes' walk.


length continuum   Also see
Lengths From Very Small
to Very Large