Dimension Diameter
The dimdiameter command places a diameter dimension on an arc or circle. The dimension line spans the full diameter — passing through the center between two diametrically opposite arc points — and is labeled ⌀ <value>. To annotate just the radius from center to one edge, use Dimension Radius.
Anatomy of a diameter dimension
●──────────── ⌀ 10.00 ────────────●
(far arc point) (near arc point / text side)
- Dimension line — spans the full diameter, with arrowheads at both arc-intersection points.
- Near arc point — the circumference point on the cursor side (where the text label sits).
- Far arc point — the diametrically opposite point.
- Label —
⌀followed by the diameter value.
Placing a diameter dimension
- Type
dimdiameterin the terminal or click the Dimension Diameter toolbar button. - Click an arc or circle to select it.
- Move the cursor to rotate the dimension line to the desired angle.
- Click to place the dimension.
Only Arc and Circle entities can be selected.
Keyboard reference
| Key | Action |
|---|---|
Escape | Cancel |
Dimension Diameter vs Dimension Radius
| Dimension Diameter | Dimension Radius | |
|---|---|---|
| Measures | Full diameter (2 × radius) | Radius (center to edge) |
| Dimension line | Edge → edge through center | Center → edge |
| Label prefix | ⌀ | R |
| Arrowheads | Two (at both arc points) | One (at arc point) |
| Best for | Full circular hole or shaft dimensions | Annotating one side of a curved feature |
DXF — DIMENSION diameter entity
Diameter dimensions are saved as DIMENSION entities with diameter-type geometry, storing both arc-point positions and the measured diameter value (2 × radius). All properties round-trip without loss.