# Metric units of length review (mm, cm, m, & km)

CCSS Math: 5.MD.A.1
Review the size of millimeters, centimeters, meters, and kilometers and how to convert between them.  Then, try some practice problems.

## Summary of metric units of distance

KilometerMeterCentimeterMillimeter
$\goldD1$$1000$$100{,}000$$1{,}000{,}000$
$\dfrac{1}{1000}$$\goldD1$$100$$1000$
$\dfrac{1}{100{,}000}$$\dfrac{1}{100}$$\goldD1$$10$

## What is distance?

Distance measures length. For example, the distance of a road is how long the road is.
In the metric system of measurement, the most common units of distance are millimeters, centimeters, meters, and kilometers.

### How big are metric units of distance?

A paper clip is about $1$ millimeter thick.
A fingernail is about $1$ centimeter wide.
The length of a guitar is about $1$ meter.
A kilometer is equal to $1000$ meters. It is a little over half of a mile.
Want to learn more about metric units of distance? Check out this video.

## Practice set 1: Estimating distance

Problem 1A
Identify the most reasonable unit to measure the distance from New York to California.
Want to try more problems like this? Check out this exercise.

## Converting larger units to smaller units

$1 \text{ centimeter} = \greenD{10}\text{ millimeters}$
$1 \text{ meter} = \greenD{100}\text{ centimeters}$
$1 \text{ meter} = \greenD{1,000}\text{ millimeters}$
$1 \text{ kilometer} = \greenD{1,000}\text{ meters}$
To convert larger units to smaller units we multiply the number of larger units by the green conversion factor for the appropriate smaller units.
Example: Converting meters to centimeters:
$1 \text{ meter} = \greenD{100}\text{ centimeters}$
$\blueD{11} \text{ meters} = \blueD{11}\times \greenD{100}=\blueD{11}\greenD{00}\text{ centimeters}$

## Converting smaller units to larger units

$1 \text{ millimeter} = \dfrac1{\purpleD{10}} \text{ centimeter}$
$1 \text{ centimeter} = \dfrac1{\purpleD{100}} \text{ meter}$
$1 \text{ meter} = \dfrac1{\purpleD{1,000}} \text{ kilometer}$
To convert smaller units to larger units we divide the number of smaller units by the purple conversion factor for the appropriate larger units.
Example: Converting meters to kilometers:
$1\text{ meter}= \dfrac1{\purpleD{1000}} \text{ kilometer}$
$\maroonD{7} \text{ m}= \dfrac{\maroonD{7}}{\purpleD{1000}} = \maroonD{7}\div\purpleD{1000}=\blueD{0.007}\text{ km}$
Want to learn more about converting between metric units of distance? Check out this video.

## Practice set 2: Converting distance units

Practice 2A
Convert.
$5$ meters $=$
millimeters
Want to try more problems like this? Check out these exercises:
Convert larger units to smaller units
Converting between units