The dimcontinue command in AutoCAD, and eight dimension commands nobody uses

Most drafters use exactly one dimension command: type DIM, pick two points, done. That works, but dimensioning a run of grid lines or a row of pile positions turns it into ten identical rounds of picking.

There are nine more commands in the set, and the dimcontinue command in AutoCAD is the one worth learning first. This article measures all nine on the same geometry, and points out where two near-identical commands put a whole chain of wrong figures on a sheet that still looks perfectly reasonable. For the full dimensioning workflow see our AutoCAD for Construction course.

Nine commands and where they live

Read from the acad.cuix interface file and the acad.pgp file of the 2027 release.

Look at the ribbon column: DIMCONTINUE and DIMBASELINE share one drop-down button, and six of the others share a second one. A drop-down is the easiest thing in the interface to pick wrongly, and the next sections show what that costs.

Chaining dimensions on from the last one

Four vertical extension lines, 1000, 1500 and 800 apart. Dimension the first gap with DIMLINEAR, then call DIMCONTINUE and pick the two remaining points.

The three real gaps, exactly. The useful part is that the first point is never picked again: each further dimension takes one pick, because the program uses the previous extension line as its origin. Autodesk's DIMCONTINUE page says exactly that: "Creates a dimension that starts from an extension line of the previous or selected dimension."

The same page spells out what it latches onto: "Automatically continues creating additional dimensions from the last linear, angular, or ordinate dimension created, or from a selected extension line." So if nothing has been dimensioned yet in the session, it asks you to pick an existing dimension to work from.

The dimbaseline command: every figure from one origin

This command looks identical, sits beside the last one in the same drop-down, and produces a completely different set of numbers.

The same four extension lines, the same picks, only the command changed:

DIMCONTINUE writes the gap between neighbouring grid lines. DIMBASELINE writes the distance from the first line to each one in turn, so the figures accumulate: 1000, then 1000 plus 1500 is 2500, then plus 800 is 3300.

Both are correct; they answer different questions. On a foundation plan, the run of dimensions closest to the building is usually a chain of gaps, while the outermost run is measured from a single datum.

The danger is that picking the wrong button still produces a tidy chain, the figures still increase sensibly, and nothing flags an error. It surfaces when somebody sets out on site.

Worth building one habit around that. After running the dimcontinue command in AutoCAD along a run of grid lines, add the figures up and compare the total against a single overall dimension across the whole run. A chain of gaps must sum to the overall; a chain measured from one datum must end on it. Thirty seconds of arithmetic catches the wrong button every time, and catches a mis-snapped pick as well.

The dimlinear command against an aligned dimension

The second pair gets confused just as often, and a 3-4-5 triangle settles it.

Build a triangle with a base of 3000, a height of 4000 and a hypotenuse of 5000.

DIMLINEAR always measures horizontally or vertically, which means it measures the projection. Put it on the hypotenuse and it gives 3000 or 4000 depending which way you drag, never 5000.

DIMALIGNED measures along the member. Roof slopes, stair strings and diagonal bracing all need it, because the figure on the drawing is the true length of the piece somebody has to cut.

This is a mistake that wastes real material: dimension a roof slope with DIMLINEAR and the purlins get cut to the projection, shorter than they need to be.

Angles and circles

Two commands that produce figures which are not distances.

DIMANGULAR measures an angle. Pick two perpendicular sides and it writes 90 degrees. It accepts two lines, an arc, or three points. Drawing and checking angles is covered in our article on drawing angles in AutoCAD.

DIMDIAMETER measures across. On a circle of radius 400 it writes 800 — the diameter, not the radius. For the radius, use DIMRADIUS. Circles are covered in our article on circles in AutoCAD.

Both of these require an object to be picked, not just a point. Run the command and click empty space and it simply asks again, with no error message to explain itself.

Editing extension lines without touching the figure

On a dense plan, extension lines end up crossing the geometry. DIMEDIT with the Oblique option slants them out of the way.

The question that matters: does slanting them change the figure?

Unchanged. The command rotates the drawn extension lines and leaves the measurement alone. That is how a drawing gets tidied without overriding figures by hand — and overriding by hand is worth avoiding, because it breaks the link between the dimension and the geometry.

Trimming extension lines short is a separate job, covered in our article on a lisp for trimming dimension lines. Setting the text size and scale of a whole dimension style is covered in our article on dimension styles in AutoCAD.

Ordinate dimensions measure position, not distance

This command differs from the other eight, which is exactly why it gets misused.

Point at a location whose X coordinate is 3000 and it writes 3000. That figure is not the distance between two points; it is the coordinate of one point relative to the current origin.

The consequence: move the origin and every figure of this kind moves with it. On a pile setting-out drawing or a steel plate fabrication drawing that is precisely what is wanted; on an architectural plan it is usually a mistake. Setting and moving the origin is covered in our article on the UCS in AutoCAD.

A centre mark is a block, not linework

The last two commands sit on the Centerlines panel of the Annotate tab, and produce something many people do not expect.

CENTERLINE builds a centre line between two lines. Tested on lines at heights of 1000 and 2000, the centre line lands exactly on 1500.

CENTERMARK marks the centre of a circle or arc. Its prompt reads Select circle or arc to add center mark or [Layer]:, and it keeps asking until you press Enter, so a dozen circles get marked in one run.

The part worth knowing: both create a block rather than plain linework. That means they stay associated with the geometry — move the circle and the mark follows — but it also means they cannot be reshaped by dragging grips the way ordinary lines can.

Five things people say that are not true

Frequently asked questions

Which command dimensions a run of grid lines?

DIMCONTINUE, alias DCO. Dimension the first gap with DIMLINEAR, then call it and give one point per grid line.

What is the difference from DIMBASELINE?

One writes the gap between neighbouring lines, the other the distance from the first line to each. Four lines 1000, 1500 and 800 apart give 1000-1500-800 and 1000-2500-3300.

How do I dimension the true length of a roof slope?

DIMALIGNED, alias DAL. It measures along the member, while DIMLINEAR only measures the projection.

Extension lines are crossing my geometry — what now?

DIMEDIT, choose Oblique, and give an angle. The dimension figure does not change.

Why does DIMDIAMETER not respond when I click?

It needs a circle or an arc to be picked. Clicking empty space makes it ask again without reporting anything.

Can I mark the centre of many circles at once?

Yes. Run CENTERMARK and click each circle in turn; it keeps asking until you press Enter.