Sketcher ConstrainRadiam

From FreeCAD Documentation

Sketcher ConstrainRadiam

Menu location
Sketch → Sketcher constraints → Constrain auto radius/diameter
Default shortcut
Introduced in version
See also
Sketcher Constrain distance, Sketcher Constrain horizontal distance, Sketcher Constrain vertical distance


This constraint automatically constrains the value of the radius/diameter of a circle or arc to have a specific value. Following rules are applied :

  • If object is a B-spline pole, a weight constrain is added
  • If object is a complete circle, a diameter constrain is added
  • In other cases (typically an arc), a radius constrain is added

If more than one circle or arc is selected before launching the command :

  • If the constrain is applied in 'Reference' mode, a new reference constrain is added to each object separately according above rules
  • If the constrain is applied in 'Normal' (driving) mode, following rules are applied
    • A reference constrain is applied separately on each object which is an external geometry
    • Equal constrains are applied sequentially between all real/construction geometry objects and a dimensional constrain is applied to the first selected object according above rules

NB : B-spline poles can't be mixed with other object type in the selection


  1. Pick one or more circles or arcs.
  2. Press the Constrain auto radius/diameter button.
  3. A pop up dialog opens to edit or confirm the value. Press OK to validate.
  4. Optionally the dimension label and line can be moved and rotated in the 3D view by clicking on the value and dragging while keeping the left mouse button pressed.

Note: the constraint tool can also be started with no prior selection. By default the command will be in continue mode to create new constraints; press the right mouse button or Esc once to quit the command.


No specific scripting applies. See the Sketcher scripting page that explains the values which can be used for ArcOrCircle and Circle, and contains further examples on how to create constraints from Python scripts.