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Dimension

In one sentence: Measures a distance, radius, or angle and displays the result with a parametric dimension line that updates when the geometry changes.

Overview

Workbench: Draft
Menu: Draft → Annotation → Dimension
Command: Draft_Dimension

Dimensions are parametric — they update automatically if you snapped to the solid geometry when creating them. Fixed-coordinate dimensions do not update.

Dimension types

Type How to create
Linear distance Pick two points, then pick the dimension line position
Radius Pick a circle or arc edge, then pick the label position
Diameter Same as radius — toggle with the Diameter button
Angular Pick two edges or three points to define the angle

Step-by-step (linear)

  1. Activate Draft → Annotation → Dimension.
  2. Pick the start point of the measurement.
  3. Pick the end point.
  4. Pick the dimension line position (how far off the measured geometry).
  5. The dimension is placed with the measured value as text.

Key properties

Property Description
Start First measurement point
End Second measurement point
Dimline Position of the dimension line
Override Optional text to override the measured value
Decimal places Number of decimal digits shown
Show unit Whether to append the unit symbol
Flip text Flip the text above/below the dimension line

Python API

import Draft

dim = Draft.make_linear_dimension(
    App.Vector(0, 0, 0),     # start
    App.Vector(100, 0, 0),   # end
    App.Vector(50, -20, 0)   # dimline position
)
App.ActiveDocument.recompute()

Common mistakes and pitfalls

Dimensions don't update after geometry changes

If a dimension was placed by clicking on free 3-D space (not snapping to an edge or vertex of a solid), it stores a fixed coordinate and will not update. Always snap to the actual edge or vertex for linked dimensions.

See also