Depending on where in the world your clients are, they most probably prefer one unit of measure to another. This may or may not match the units you have on your rates. Defining your default units of measure is quick, easy and can be changed at any time. 

Select Preferences from under the username in the top right corner of your screen.

A screen will appear with two sections: Basic Preferences such as language, country and number formatting, and Preferred units.

Choose to change any or all of the preferred units. This will set the default units for all of your quotes. At any time you can change the default units, or you can change the units on each individual quote.