Our surveyor's formula tool is derived from the surveyor's formula described by Chris Fisher in response to a question on finding the area of a polygon. It was implementated in an Excel spreadsheet by Stephen La Rocque.
To use this tool your property needs to have the shape of a polygon, and you need the lengths of the sides and their bearings. The most likely place to find these dimensions is on a surveyor's drawing.
Input the side lengths and bearings going around the property in a counterclockwise direction as in the example below.
The column labeled dir for direction should have the value CW or CCW depending on whether the bearings are measured in a clockwise or counterclockwise direction.
You can download the Excel spreadsheet, view the above example in its entirety, or view the 17 sided lot that motivated Stephen to construct the spreadsheet.