If a border doesn't already exist around the area you want to measure, do one of the following:
Create a border around a single shape
Use one of the drawing tools to create a border around the area's perimeter.
Note To create a closed shape, make sure the first and last vertices of any shape you draw are connected.
Create a border around multiple shapes
Do one of the following:
Use the Pencil tool to trace the boundary of all the shapes, and then find the shape area and perimeter of the simple boundary.To measure multiple areas, draw a separate border around the perimeter of each area.
Note To create a closed shape, make sure that the first and last vertices of any shape you draw are connected.
Create a border that subtracts space you don't want to measure
When you find the shape area and perimeter, the area of the hole is subtrracted from the total area.
Select the closed shape or shapes you want to measure.On the Tools menu, point to Add-Ons, point to Visio Extras, and then click Shape Area and Perimeter.From the Total area and Total perimeter lists, select the units of measure you want.
If you select multiple shapes, the Total area and Total perimeter values reflect all the shapes combined.
With the Shape Area and Perimeter dialog box still open, resize the shapes you are measuring, or select different shapes on the drawing page. The area and perimeter values are updated automatically.When you have finished, click Done.
To display the text on the drawing page, select the text in the Total area or Total perimeter box, copy the text, and paste it onto the drawing page.
You can see the area to be measured by applying a fill pattern to the shape. For example, to verify that areas in the shape have been subtracted properly, apply a fill pattern. If the fill pattern doesn't define the area you want to measure, your borders or shapes may not be closed. Close them and try again.