A pair of parallel lines in AutoCAD is the thing you draw most often in a building plan. Every wall is two parallel lines, and so is every plaster layer and every inner outline of a floor plan.
Most guides name one command and stop there. This article gathers four routes, says plainly which suits which moment, and spends a whole section on the place people get stuck that no page explains properly. For the full drafting and documentation workflow, see the AutoCAD for Construction course.
Which route to pick for parallel lines in AutoCAD
All four routes below produce a parallel line. What separates them is what you already know when you start.
| Route | Use it when | Type |
|---|---|---|
OFFSET | You have the source and the distance | O |
MLINE | You need two or more lines at once | ML |
Parallel object snap | You do not know the source angle | F3, then tick it |
XLINE with Offset | You need an endless guide line | XL then O |
Only OFFSET remembers the distance you just used. The other three ask again every time you call them.
Where to start the offset command
Four ways in, read straight out of the 2027 configuration files.
| Route | Detail |
|---|---|
| Full command | OFFSET |
| Alias | O |
| Ribbon | Home → Modify → Offset |
| Classic menu | Modify → Offset |
| Toolbar | Modify → Offset |
A single-letter alias, O, and a button of its own in all three other places.
The prompts, step by step
Before asking anything the program prints a status line, copied verbatim: Current settings: Erase source=No Layer=Source OFFSETGAPTYPE=0.
| Step | What the program asks | What you do |
|---|---|---|
| 1 | Specify offset distance or [Through/Erase/Layer] <300.0>: | Type the distance and press Enter |
| 2 | Select object to offset or [Exit/Undo] <Exit>: | Click the source line |
| 3 | Specify point on side to offset or [Exit/Multiple/Undo] <Exit>: | Click any point on the side you want the copy |
| 4 | back to the step 2 prompt | Click the next object, or Enter to finish |
Three things follow.
Step 3 only needs a point on the right side, not a precise position. The program reads which side, not how far from that point.
Steps 2 and 3 repeat, so the distance is entered once and then any number of parallels follow.
Typing M at step 3 enters multiple mode: every further click adds another copy, each one the same distance beyond the last. It is the quickest way to build a run of evenly spaced lines.
The offset command in AutoCAD: the real prompts and three options
The Autodesk OFFSET page describes the command in one line: "Creates concentric circles, parallel lines, and parallel curves". The new object always keeps the type of the old one.
The first thing the command does is print the three settings currently in force. Reading that line before you do anything saves work later on.
Current settings: Erase source=No Layer=Source OFFSETGAPTYPE=0
Specify offset distance or [Through/Erase/Layer] <Through>:
Once it has a distance, the command asks two questions over and over. Which object, and which side the new one goes.
Select object to offset or [Exit/Undo] <Exit>:
Specify point on side to offset or [Exit/Multiple/Undo] <Exit>:
Those lines are copied verbatim from AutoCAD 2027 at the Institute.
The three words in square brackets are three unrelated jobs:
- Through skips the number entirely. You pick the object, then pick a point, and the new object runs through it. Autodesk adds a note few people know: put that point near the middle of a segment, not near a corner.
- Erase deletes the source after the copy is made, which suits moving a line inward rather than duplicating it.
- Layer decides whether the new object lands on the source layer or the current one. If you see
Layer=Currentwhile drawing walls, switch back toSourcestraight away.
Notice that the default in the prompt above is the word <Through> rather than a number. That happens because OFFSETDIST is holding a negative value. Autodesk states it plainly: below 0 the command takes the through-point route, and 0 or above is a stored distance. One use of Through sets it negative, and the next call looks as though AutoCAD forgot the old number.
Draw parallel lines in AutoCAD at even spacing with Multiple
No prompt anywhere in the command asks how many copies you want. The option that does that work is Multiple, and it only appears after you have picked an object.
Type M at the third prompt and every click adds another line. The detail people miss: the second line is measured from the first, not from the source, so four clicks at a distance of 100 give lines at 100, 200, 300 and 400.
The command repeats for your convenience: pick one object and it asks for the next. Autodesk says so outright — "The OFFSET command repeats for convenience. To exit the command, press Enter".
The parallel object snap in AutoCAD when you do not know the angle
Almost no guide mentions this route, and yet it is exactly right when you need a new line parallel to an existing one whose slope you never measured.
Type OSNAP to open the dialog above and tick Parallel at the bottom of the right column. It behaves unlike every other snap mode, and the Autodesk reference sets out three steps:
- Start
LINEand pick the first point first. Without a first point the mode does nothing. - Hover the cursor over the old line and pause until the angle is acquired.
- Move back toward the line you are drawing. When the path matches, an alignment path appears and you click the second point on it.
One condition is easy to forget: Ortho must be off. The documentation says so, and object snap tracking and polar snap switch themselves off while the mode is working. It accepts a line, a polyline segment, a ray or an xline. The remaining snap modes are covered in object snap in AutoCAD.
The MLINE command in AutoCAD for a two-faced wall
When what you want is two lines at once rather than one line added to another, MLINE does it in a single pass. The MLINE page sums it up in four words: "Creates multiple parallel lines".
The default STANDARD style declares two lines at 0.5 and -0.5, exactly one unit apart. Scale multiplies that figure, so a scale of 200 gives a wall 200 thick. Justification decides whether the point you click lands on the top line, the centre or the bottom one; pick Zero to draw along the wall centre.
These three live in the variables CMLSCALE, CMLJUST and CMLSTYLE. Set them once and later calls keep them. On a fresh drawing they read 20, 0 and STANDARD.
Two details Autodesk notes here have no equivalent in OFFSET: a negative scale flips the order of the lines, and a scale of 0 collapses the whole set into a single line. Against OFFSET, which refuses every non-positive number outright, that is a real difference.
The trade is that a multiline is harder to edit than loose lines. Two multilines crossing do not trim each other, so you need MLEDIT. For a house full of doors and service ducts, loose lines edited with TRIM and FILLET still move faster.
Cannot offset that object: three refusals and what they mean
The pages ranking at the top of search answer this only in general terms, so here it is in full.
Type 0 or a negative number as the distance and the answer comes back at the distance prompt itself.
Specify offset distance or [Through/Erase/Layer] <100.0000>: -50
Value must be positive and nonzero.
The distance carries magnitude only. Which side you get comes from where you click, not from the sign of the number. That disposes of the advice, still passed around, that a negative figure puts the copy on the other side.
The second message is harder, because one line of text covers two unrelated causes. Four different objects, one after the other. Where the message appears is what separates them:
| What you picked | The message | When it appears |
|---|---|---|
| A single line of text | Cannot offset that object. | Right after you pick, with no side prompt |
| A hatch | Cannot offset that object. | Right after you pick, with no side prompt |
| A circle of radius 100, pushed inward 200 | Cannot offset that object. | Only after you point to a side |
The first two rows are about object type: text, hatches and blocks do not take this command, so change the object rather than the number. The last row has a perfectly valid object type, and the trouble is that the result cannot exist. Push a circle of radius 100 inward by 200 and there is no circle left to draw. Reduce the figure instead of swapping the object.
That distinction saves real time. If the refusal arrives before you even point to a side, there is no use trying other numbers.
OFFSETGAPTYPE decides how the outside corner closes
Push a bent outline outward and every convex corner opens a gap, because the two new segments no longer meet. OFFSETGAPTYPE decides how that gap is filled.
Value 0 extends both segments until they meet, keeping the corner sharp. Value 1 fillets it, with a radius equal to the offset distance. Value 2 chamfers it. On the machine at the Institute the variable reads 0, which is the shipped default.
One point is easy to get wrong. The OFFSETGAPTYPE page records it as saved in the registry, so it follows the machine rather than the file. It does not travel with a drawing you send, and a drawing you receive does not carry the sender's setting.
Offsetting inward is a different story. About Offsetting Objects states that polylines and splines are trimmed automatically when the distance is larger than the shape can take, and that segments may be deleted outright. The practical upshot: when you build a plaster layer or an inner outline, check the narrow places. Anything thinner than twice the offset distance disappears, and the drawing still looks normal.
Four things often repeated that are not true
| What you often hear | What AutoCAD 2027 actually does |
|---|---|
| Type a negative number to put the copy on the other side | The answer is Value must be positive and nonzero. Pick the object again and click the other side |
| Type a quantity to create several copies at once | No prompt asks for a quantity. That job belongs to Multiple |
| There is a "Double Offset" command for both sides at once | Typing DOUBLEOFFSET returns Unknown command. It is the name of an external LISP file, not a command |
An open polyline needs PEDIT to close it before offsetting | Open polylines offset perfectly well, with nothing to convert |
The last two rows deserve a note. On AutoCAD 2027 with Express Tools installed, DOUBLEOFFSET and DOFFSET both return Unknown command, exactly as a made-up name does. A page currently ranking on the first search page calls it "the Double Offset command", and readers will type it forever without result.
Frequently asked questions
What is the keyboard shortcut for the offset command in AutoCAD?
The letter O, then Enter. The matching button sits in the Modify panel of the Home tab.
Why can I not see the new object after offsetting?
Usually it landed on a layer that is turned off. Check the status line at the start of the command: Layer=Current means the copy follows the current layer, not the source layer.
What do you get when you offset an ellipse?
A spline, not an ellipse, because the curve at a constant distance from an ellipse is mathematically no longer an ellipse. The detail sits in drawing an ellipse in CAD.
How is offsetting different from scaling?
Completely different. SCALE multiplies coordinates by a factor, so the new shape is always similar to the old one. OFFSET moves every edge by the same distance, so a short edge can be swallowed by its neighbours and the shape changes.
What is the fastest way to draw two parallel lines in AutoCAD?
Draw one line and run OFFSET once. If dozens of walls share a thickness, set up an MLINE style and draw with that instead.
Can I make two lines stay parallel afterwards?
Yes, with the Parallel geometric constraint from GEOMCONSTRAINT. It does more than draw once: it holds the relationship, so editing one line moves the other.