# Choosing Appropriate Units of Measure

In the physical world around us, we come across the quantities such as time, distance, mass, area, volume, and so on. In a mathematics course, we are more interested in the units of measurements, which are used to describe the magnitude of each of these quantities.

Some units of measurement are given below:

 Time Distance (Metric) Distance (Customary) Mass (Metric) Weight (Customary) Second Millimeter Inch Milligram Ounce Minute Centimeter Foot Gram Pound Hour Meter Yard Kilogram Ton Day Kilometer Mile Metric Ton Month Year Century

While describing various physical quantities, it is best to use appropriate units of measure. Using other units of measure to describe a quantity gives either very small or very large number value. It becomes difficult to estimate the magnitude of the quantity, if inappropriate units are used.

 Quantity Appropriate unit of measure Distance between two cities Miles or kilometers Height of a person Feet and inches, or centimeters Weight of a person Pounds or kilograms Height of a high-rise building Meters or feet Height of a mountain peak Meters or feet Depth of a ocean Meters or feet Area of a football field Feet$2$ or meters$2$ Capacity of milk bottle Liters Size of a Paper Inches or centimeters Time taken to complete $100$ meter race Seconds Time taken to travel between two cities by car Hours

Example:

What is the appropriate unit of measure used to describe the width of a computer monitor?

The width of computer monitor is usually between $10$ inches and $20$ inches.
We know that $1\text{inch}=$ $2.54$ centimeters. So, when these values are converted to centimeters, it is about $25$ and $50$.
Very small numbers (less than $1$) are needed to express the width of the computer in feet or meters. So, it is not possible to accurately measure the width of computer monitor in feet or meters.