Acreage Calculator - Measure the area of a plot of land
The easiest way to measure the area of a plot of land is to start by entering an address that is associated with the plot of land you need the area of. In rural areas where an address may not be available, you can enter the cross street or even the GPS coordinate of a point on the land. For GPS coordinates be sure to enter the latitude followed a comma then the longitude ex. (41.87811, -87.629798). In any case this will place a marker that you can use as a reference point to draw the area on the map. Once you are finished drawing the area calculator will display the area of the shape above the map.
How to use the google maps area calculator tool to measure a roof
Special precautions must be taken when measuring the area of a roof. The images that appear on google maps are often at a slight angle, which combined with the angle of a roof can cause errors. For this reason it is best to outline the roof at points which are all at the same elevation. On a simple house for instance you would only click on the corners of the roof and not on any points along the peak as that would cause an error. After measuring the area of the footprint you can estimate the actual roof area based on the angle of the roof. Similarly if you using the area calculator tool to measure a roof with multiple levels, you should do the individual section separately.
The google maps area calculator is not 100% accurate. Do not rely on this tool as your only resource in making important decisions.