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 |
Editing the label — simple mode
Double-click a placed diameter dimension to open the text editor in simple mode. The editor is pre-seeded with the current rendered value (e.g. ⌀ 10.00) so you can position the cursor and edit it directly.
| Feature | Behaviour |
|---|---|
| Bold / Italic / Font / Height | Apply to the entire label at once |
| Per-character formatting | Not supported |
Enter | Commits the value and closes the editor |
| Multi-line | Not supported |
See Text Editor — simple mode for the full reference.
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.
Unit format and precision
The Unit Format property in the property window chooses how the measurement is written: Scientific, Decimal (the default), Engineering, Architectural, Fractional, or System, which follows your system’s number style. Precision lists its choices the way the chosen format writes them — fractions of an inch for Architectural and Fractional, for example. A DXF’s own unit format is read in, and new dimensions take both settings from the current DimensionStyle. Fractions are written on one line, not stacked.
Dimension style
New diameter dimensions copy the current DimensionStyle, including separate arrowheads, center-mark type and size, text, precision, gap, alignment, and frame. Outside dimensions use the second arrowhead consistently and begin the outside leader at the circle or arc.