Length is a measure of how long something is from end to end.  This may include distance, which means the space between two points or objects.  When you measure the distance around an object, this gives you the perimeter.


Units are used to measure the length and distance.  There are two systems of measurement: the Metric System and U.S. Customary System.

When To Use Which Type Of Unit

To measure very short lengths, such as the length of your thumb or one of your toes, we usually use centimeters or inches.


When we want to measure longer lengths or distances, we usually use meters, feet, or yards.  Some examples would be the height of a fence or the length of a football field.


When we measure longer distances, we use kilometers or miles, like measuring the distance from your house to your school or the height of a tall mountain.

Table of Length Conversions
U.S. Customary Unit
Metric System