APPENDIX
E Measurement ............................................................................
Throughout this book, you’ve encountered units of measurement from both the customary and
the metric system. This appendix covers the key information you need to function in each system
and just a word or two about shifting from one to the other. In each system, you measure three
basic quantities: length (or distance), mass (which, with gravity, determines weight), and volume.
Metric System
The metric system of measurement (also called the International System of Units) is used around
the world, and its popularity likely stems not just from the idea of a universal system but from
the consistent decimal logic of the system. Everything is based on tens. There are base units of
length, mass, and capacity. The larger and smaller units are created by dividing a base unit by 10
or 100 or 1,000 (and so on) or by multiplying by 10 or 100 or 1,000 (and so on).
Basic Unit Approximation Official Definition
Length: meter The distance from a doorknob
to the floor
The path length travelled by
light in a given time
Mass: gram* The mass of a paperclip The mass of one cubic
centimeter of water at 4°C
Capacity: liter The volume of a medium-
sized bottle of soda or water
The capacity of a container
with a volume of 1,000 cubic
centimeters
*The current standard defines the kilogram as the base unit and the gram as one one-thousandth of a kilogram, but
the system is easier to understand if you begin with gram, the original base unit.
