US Standard Lengths

Measuring how long things are, how tall they are, or how far apart they might be are all examples of length measurements.

8 inches fork
Example: This fork is 8 inches long

These are the most common measurements:



Small units of length are called inches. 

The last joint of your finger or thumb is about 1 inch (depending on how big your fingers are!).

An inch is defined as exactly 2.54 centimeters (a metric measurement)

Lots of things are measured in inches from rainfall to paper length.

Measuring in inches gives us a way for everyone to understand the size of something. 



When we have 12 inches together, it is known as a foot. 

1 foot = 12 inches

A long time ago, people used their feet to measure things.  But everyone has different sized feet so it did not work very well. 

Using 12 inches put together to make one foot lets everyone have an accurate picture of what exactly a "foot" of length is.


1 meter

When 3 feet are together, it is called a yard

(This isn’t the same thing as a garden, though they are both referred to as a "yard"!) 

1 yard = 3 feet

The length of this guitar is about 1 yard.




When we put together 1,760 yards, we have a mile.

1 mile = 1,760 yards = 5,280 feet

Miles are long distances and are mostly used to measure the distance between places which are far away from each other.  Most people refer to miles when they are driving, biking or jogging.

To remember how many feet in a mile think:

Five tomato
Five two eight oh
5,280 feet in a mile


Final thoughts about measuring length:

1 foot = 12 inches

1 yard = 3 feet = 36 inches

1 mile = 1,760 yards = 5,280 feet = 63,360 inches

From Miles to Kilometers

A mile is exactly 1.609344 kilometers. Yes, the mile has a metric definition.

Example: what is 55 miles in kilometers?

55 miles × 1.609344 km/mile = 88.51392 km

Quick but not accurate Conversions

Here is a funny thing! These numbers can help us do conversions:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ...

It is the Fibonacci Sequence, which is made by adding the two previous numbers each time. Example: 5+8=13, 8+13=21, etc.

Its pairs of numbers can help us
convert between miles and kilometers.

The first few numbers don't work well, but let's look at "3, 5":

3 Miles is About 5 km (3×1.609344 = 4.828032)

And "5, 8": 5 Miles is About 8 km (5×1.609344 = 8.04672)

And "8, 13": 8 Miles is About 13 km (8×1.609344 = 12.874752)

And so on.

(Why? Because the ratio between pairs of numbers gets closer and closer to the Golden Ratio of 1.6180... which just happens to be nearly 1.609344)


Lots of Examples

An inch is:

A foot is:

A yard is about:

A mile is about:


Activity: Discover Lengths