Google Earth is a free software application that provides a bird's eye view of the world with detailed aerial and satellite photography covering the entire surface of the Earth. Although zooming in on interesting landmarks, exotic cities or favorite places is an entertaining way to spend a few minutes, Google Earth is also a useful planning and research tool. The program contains all the tools you need to measure distances and estimate sizes of any feature on the surface of the planet. To measure the acreage of land in Google Earth, use the "Ruler" tool and select "Acres" as the measurement unit.
Launch Google Earth by double-clicking its icon on the computer's desktop screen.
Find the surface feature you wish to measure by entering its name, address or ZIP code in the Google Earth search box.
Position the feature and zoom in or out so that it's contained within the 3D viewer screen. Click "U" on the computer keyboard to ensure the view of the land is top down.
Select "Ruler" from the "Tools" menu. This opens the "Ruler" dialog box. Move the box to an area of the screen that doesn't obscure the viewer.
Select the type of shape that you wish to measure with -- either the "Line" or "Path" option. Choose "Acres" as the unit of measure.
Click on the viewer with the mouse cursor to mark the start point for the measurement. For example, if you're measuring a field, click on one corner of the field. As you move the mouse cursor away from this point, a line extends from the start point to the position of the cursor. Click again when you need to turn a corner; this will add a new line from the second click point. Continue to click around the perimeter of the feature until the line or path shape measures the entire region.
Check the "Ruler" dialog box at the end of the process for the acreage of the shape you have measured.
Users of the paid Google Earth Pro software can choose polygon and circle shapes, in addition to the line and path shapes, to measure objects.