In 3D mode there are two independent ways to see a part's dimensions: the always-on dimensions panel and the manual measuring ruler.
Dimensions panel
Enabled by default. Shows overall dimension lines along the X/Y/Z axes and coordinate leaders for each operation. Labels that coincide on a coordinate are automatically laid out to avoid overlapping; when viewed strictly end-on, where all labels project onto one line, they are additionally "pushed apart" for the current angle. Hovering over the dimension line itself (not an operation) shows a tooltip explaining what it displays (length, width, thickness, or a specific operation's coordinate).
Dimensions are automatically hidden while rotating with the mouse and while the measuring ruler is active, so they don't get in the way.
Measuring ruler
- Click the ruler button in the toolbar.
- Click a face of the part — the model turns to face it perpendicularly, and rotation is temporarily locked.
- Click points on that plane — a polyline with the distance in millimeters is built between them. The first segment is labeled with just its length; from the second segment on, it's labeled with that segment's length and the running total.
- To reset the measurement, press Alt+Q.
- Clicking the ruler button again turns off the mode and returns to the isometric view.