The array command in AutoCAD copies a shape into rows and columns or around a centre. Everybody knows that. What fewer people know is that for several releases it has not produced loose copies at all.
This article counts the objects to show exactly what the difference is, measured on AutoCAD 2027 at the Institute. For the full set of drafting shortcuts, see the AutoCAD for Construction course.
Two arrays that look identical, with a different object count
Autodesk's ARRAYRECT page describes the command in one line: "Distributes object copies into any combination of rows, columns, and levels." We drew one circle, built an array of four rows by three columns, and counted the objects created. Then we repeated it with the ARRAYASSOCIATIVITY system variable set to 0.
ARRAYASSOCIATIVITY | Objects created | Object type |
|---|---|---|
| 1 (default) | 1 | INSERT |
| 0 | 11 | loose circles |
The first row is the surprise. Twelve circles on screen and, in the file, one object, of type INSERT — a block reference.
To get loose copies instead, set ARRAYASSOCIATIVITY to 0 before building, or choose ASsociative inside the command and answer no. Any way you take the object count it comes out the same: click one circle in an associative array and all twelve highlight, because they are one thing.
What an associative array gains and loses
Autodesk states the two states plainly. Yes "Contains array items in a single array object, similar to a block", while No "Creates array items as independent objects. Changes to one item do not affect the other items."
The phrase similar to a block explains exactly the type we measured: INSERT.
Both kinds have their place, so knowing the trade-off is what matters.
| Associative array | Loose array | |
|---|---|---|
| Changing rows or columns | drag one grip | delete and rebuild |
| Editing one item | needs the in-array edit mode | edit it like any object |
| Objects in the file | one | one per item |
| Deleting one item | not directly | delete like any object |
The great advantage of the associative kind is that it stays editable. A row of piles turns out to need one more line: select the array, drag a grip, done.
The disadvantage is just as clear. If one corner pile has to go because it clashes with a pile cap, the associative array is in the way and has to be exploded.
Three array commands, not one
AutoCAD has three separate commands rather than the single dialog of older releases.
| Command | Array type | Used for |
|---|---|---|
ARRAYRECT | rows and columns | pile grids, column grids, floor tiles |
ARRAYPOLAR | around a centre | bolts around a flange, chairs around a round table |
ARRAYPATH | along a path | trees along a kerb, sleepers along a rail |
Typing AR runs the general command and it asks which type. Typing the full name goes straight to that type, one step quicker.
The rectangular prompts, copied verbatim from the 2027 release.
Type = Rectangular Associative = Yes
Specify opposite corner for number of items or [Base point/Angle/Count] <Count>:
Enter number of rows or [Expression] <4>:
Enter number of columns or [Expression] <4>:
Specify the distance between rows or [Expression] <720.0>:
Specify the distance between columns or [Expression] <720.0>:
That first line says straight away whether the array will be associative. Reading it before going further saves a good deal of rebuilding.
The four lines after it hold a small trap we walked into ourselves while measuring this article. The command asks for rows before columns, which is the reverse of the way most people describe a grid out loud. Typing the numbers in the order you were thinking them gives an array with the right item count and the wrong shape, and the two spacings swap over with them. Reading the prompt instead of typing from memory is the whole fix.
The Expression option: type a formula instead of a number
The word Expression in the brackets is one almost nobody uses, and it solves the most common problem of all.
Instead of typing a count, type a formula. To spread piles across 24000 at 1500 centres, type 24000/1500 at the column count prompt and AutoCAD works out 16.
Autodesk describes it in one line: "Derives the value based on a mathematical formula or equation." The benefit is not saving a trip to the calculator. It is that you record your intention — a length divided by a spacing, rather than a 16 that came from nowhere. Change the pile spacing later and you know exactly what to recompute.
What exploding an array gives you
The practical question when one item has to change. We exploded an associative array of four rows by three columns and counted again.
| Before exploding | After exploding |
|---|---|
| 1 object | 12 objects |
Twelve loose circles, exactly the item count. There is no way back afterwards, so it is worth a moment's thought. The block definition the array created stays behind in the drawing too, unused from that point on, which is one more reason to purge after any session that explodes arrays.
The less destructive route is the in-array edit mode. Select the array and the ribbon offers a button for editing a single item, letting you change one while the array remains an array. Managing blocks and attributes is covered in our article on blocks in AutoCAD.
Why the object count says block reference
The measurement shows the object type is INSERT, a block reference, and that explains several puzzling behaviours.
It explains why clicking one item highlights the whole array: you are selecting a block, not a circle.
It explains why an array is so much lighter than copying by hand: the file stores one definition plus a rule for distributing it, not twelve circles.
And it explains why cleaning a drawing needs care. An associative array creates a block definition with an automatic name. The purge command leaves it alone while the array exists, but exploding the array makes that definition surplus. Cleaning up is covered in our article on making a DWG lighter.
Where the array command in AutoCAD beats copying by hand
Three situations make the difference obvious, and all three come up weekly on construction documents.
A pile grid that is still being negotiated. The engineer says eight by six today and nine by six tomorrow. An array takes a grip drag; copies taken by hand take an afternoon.
A façade with a repeating module. Window, pier, window, pier across thirty metres. The Expression option turns the length and the module into a count without arithmetic.
Anything measured from a centre line. A polar array holds the geometry exactly on the radius. Copies rotated by hand drift, and the drift only shows up when somebody dimensions it.
The one case where copying by hand still wins is a run of items that are nearly but not quite regular — a row of columns where two have to shift for a stair. There, an array creates more work than it saves, because every exception has to be edited inside the array afterwards.
Polar arrays and path arrays
The other two types get less attention but answer very specific questions in construction documents.
A polar array asks for a centre, an item count and an angle to fill. The setting worth remembering decides whether items rotate as they go round. Bolts around a flange should rotate; level markers around a circular court should not, because the text must stay upright.
A path array distributes items along an existing object, curves included. It asks whether to divide evenly or keep a fixed spacing. Divide evenly and the spacing stretches to fit; keep the spacing and the remainder falls at the end.
Street trees along a curved kerb are the classic case. Draw the kerb line as a polyline, distribute the tree block along it, and when the kerb line changes the array follows, because it is associated with that object.
That is also the argument for using an associative array here. A loose one means starting again every time the alignment moves.
Three things often repeated that are not true
| Often repeated | What we measured on the 2027 release |
|---|---|
| The array command makes loose copies | An associative array creates one object, of type INSERT |
| Once built, the row count cannot change | Drag a grip on an associative array and rows, columns and spacing all change |
| Editing one item means exploding the array | There is an edit mode that leaves the array intact |
Frequently asked questions
What does the AR alias do?
It runs ARRAY, which then asks for the type. Typing ARRAYRECT or ARRAYPOLAR goes straight there.
Why does clicking one item select the whole array?
Because an associative array is a single object of type INSERT. We read the type and counted exactly one.
How many objects does exploding give?
Exactly the item count. A three-by-four array explodes into 12 objects; we counted and got that number.
Does an associative array make the file heavier?
The opposite. The file stores one definition and a distribution rule rather than every copy, which matters on a pile grid of several hundred items.
When is copying by hand still better?
When the run is nearly but not quite regular. A row of columns where two shift for a stair costs more to fix inside an array than to copy by hand in the first place.
Can the count be derived from a length?
Yes, with the Expression option. Type the division straight in, for example 24000/1500, at the count prompt.