The overall dimension scale is set on the Fit tab of the New, Modify, or Override Dimension Style dialog boxes (see “Fitting Dimension Text and Arrowheads”). The scale changes the size of the dimension geometry relative to the drawing. AutoCAD multiplies the geometric dimension values, such as text height, arrowhead size, offsets and gaps, by the overall scale value. In general, you should set the dimension geometric values to their plotted size, and use the overall scale to compensate for layout scaling. AutoCAD does not apply the overall scale to tolerance values, coordinates, or angles.
Relation between dimension scaling, plot scale, and output text height
When you set the overall dimension scale, you can enter a value or you can choose Scale Dimensions to Layout to have AutoCAD scale dimensions based on the scale of the layout view. If you work directly in a layout, AutoCAD uses the default scale of 1.0. If you choose to scale in layouts only, AutoCAD computes the scale automatically, and the overall scale option is not available.
The dimension scale is independent of the drawing scale, although they should be identical. For more information about the drawing scale, see “Setting Grid Limits.” Changing the drawing scale might cause dimension text and arrowheads to appear at inappropriate sizes. Set text height and arrowhead size to the actual sizes you want. AutoCAD multiplies these values by the overall dimension scale.