To Customize Sheet Scale

1. Open the 2D sheet you want to use. If your project contains several sheets or models, use the Project Browser to select a 2D sheet.
2. Click View tab Workspace panel Windows drop down Set Scale by Measure New Measure.
3. On the 2D sheet, trace a line of geometry. Choose a line that you know the length of.
4. In the Enter Value dialog, type the known length and measurement unit, then click OK. The average scale appears in the Set Scale by Measurement window. If necessary, repeat to trace several lines for a more accurate scale.
5. Press Delete or right-click a row Delete to delete a scale record.