AutoCAD FAQ

This problem arises from incompatibility between drawing units set in the drawing used to create the original block (the source drawing) and the drawing the block is imported into (the target drawing).

When a block is imported into a target drawing, AutoCAD automatically scales the block to fit the target drawing. The scale factor used is calculated as a ratio between the drawing units set in both the source drawing and the target drawing. If the drawings units are set incorrectly in either drawing, then the AutoCAD calculated scaling factor will be incorrect. As a result, the block will insert at the wrong size.

Drawing units are controlled by the variable INSUNITS. This variable must to be set in both the source drawing and the target drawing. There are 21 available values for this variable:

This variable can also be set by selecting the menu FormatUnitsInsertion Scale and choosing a unit from the list.

The easiest way to ensure insertion scales do not conflict, is to draw all drawings using the same units, and have the variable INSUNITS set to 0. This ensures that no scaling occurs and the blocks are inserted at the correct size.

If it is not possible to change the variable INSUNITS in the source drawing, there are two more variables that affect the insertion scale of blocks. These variables are both set in the target drawing and they only function if INSUNITS is set to 0.

1. The variable INSUNITSDEFSOURCE defines what unit the source drawing (the block) is drawn in. The available settings are the same as for INSUNITS.

2. The variable INSUNITSDEFTARGET temporarily assigns a drawing unit to the target drawing. This only affects scaling of the block and not the target drawing as a whole. The available settings are the same as for INSUNITS.