Setting the scale for each page in a project before starting takeoff is of utmost importance. Even though the page may indicate a particular scale, it is critical that you verify that the listed scale is accurate. A small discrepancy in the scale of a displayed image can affect takeoff quantities - especially as a project gets larger, see Verifying the Scale of an Image.
Plans sets may have different scales for different pages. Each page, however, can be assigned only one scale. If there are several regions on a particular page that are drawn to different scales, duplicate the page and set each copy to a different scale, see Dual or Multiple Scales on the Same Page for instructions.
Changing the scale of a page after performing takeoff is not recommended as On-Screen Takeoff may not be able to resize existing takeoff correctly - some takeoff objects may no longer fit on the page or on their parent objects.
When a new, blank page is added to a project, the page size and scale is automatically set based on New Bid Options. When adding a page linked to an image file, On-Screen Takeoff attempts to extract the page size/scale from the properties of the image file.
To change the scale of a page:
From the Image Tab, use the Scale drop down on the Settings toolbar to select the scale.
Using any of the above methods, select "Custom Scale" and enter the dimensions.
For Imperial measurements, the quantities are entered in feet and inches
For Metric measurements, the quantity is entered in millimeters