Editing Dimension Tolerance Properties

This task explains how to access and edit dimension tolerance properties.

There are different types of tolerances:

  • Numerical tolerances 
  • Alphanumerical tolerances


  • Combined tolerances (an alphanumerical value and two numerical values): ISOCOMB tolerance.


Open the Brackets_views02.CATDrawing document. Create a diameter dimension, for example.
  1. Select the diameter dimension.

  2. Select Edit> Properties and click the Tolerance tab.

You can also right-click the dimension and then select Properties from the displayed contextual menu.

  1. You can associate a tolerance to the selected dimension. In this example, choose ISOALPH1 in the Main Value field. 

The First value field is enabled and displays an alphanumerical value. The corresponding numerical equivalents are displayed in the Upper value and Lower value fields. (These equivalents are defined by standards.)

  1. Assign the desired tolerance to this dimension by selecting another alphanumerical value. In this example, select H9 in the First value field.  The corresponding numerical equivalents are automatically displayed.

  2. In some cases, you may wish to display another tolerance. In this case, select a tolerance type in the Dual Value field. 

  • If you choose the same tolerance type for main and for dual value, then the values for this tolerance will also be the same. 
  • For a full description of the tolerance type selected in the Main Value and Dual Value fields, click the information (i) icon in front of each field.


  1. Click OK to validate and exit the dialog box.

  • For dimensions with alphanumerical tolerances, you can display the corresponding numerical equivalents in the drawing, simply by selecting the dimension and placing the cursor over the tolerance in the drawing. The numerical equivalents are displayed in a tooltip.
  • For dimensions with tolerance js and JS, there is no correspondence between the numerical and alpha numerical value. The numerical value displayed is +-0 or the previous numerical value applied to the dimension.