Draftsight allow us to perform mathematical and trigonometric computations and measurement unit conversions using SmartCalculator feature.
You can access the calculator via Manage -> Utilities -> Smart Calculator. Alternately, you can type SMARTCALCULATOR in command window.
The Smart Calculator will be display as following:
To convert units of measurement:
a. Select a Units type (you can choose between Length; Area; Volume; Angular)
b. Select the unit you want to Convert from.
c. Select the unit you want to Convert to.
d. Type the Value to convert.
e. Click Evaluate 
.
The result displays in Converted value.