How-to guide · how to mirror a block in autocad
How to mirror a block in AutoCAD
By Saumyajit Maity · Published 29 Aug 2023 · Updated 17 Jul 2024
Mirroring is how you flip a door swing, create the opposite hand of a layout, or lay out a symmetrical room without redrawing a thing. In AutoCAD the MIRROR command reflects any object — including a block — across a line you define, and it takes about five seconds once you know the prompts.
The catch that bites everyone is text. Mirror a block carrying labels or attributes carelessly and the text comes out reversed and unreadable. This guide covers the basic mirror, the MIRRTEXT system variable that keeps text the right way round, and the practical uses — opposite-hand rooms, symmetrical furniture, door and window flips — where mirroring saves the most time.
Get the mirror line and MIRRTEXT right and mirroring becomes one of your most-used edits. It is the fastest route to symmetry in the whole program.
How the MIRROR command works
MIRROR reflects selected objects across a mirror line that you define with two points. Everything on one side is flipped to the other, as if folded across that line. The mirror line can run at any angle, so you can mirror horizontally, vertically or along a diagonal wall.
A block reference mirrors as a unit — the whole symbol flips together, which is exactly what you want for a door, a chair or a vehicle. The block's insertion point does not have to lie on the mirror line; AutoCAD reflects the geometry wherever it sits relative to the line you draw.
Step 1 — Select the block and start MIRROR
Select the block (or several objects) first, or start the command and select after. Type MIRROR (or MI) and press Enter. If you haven't pre-selected, AutoCAD prompts 'Select objects' — click the block and press Enter to confirm the selection.
For a clean mirror it helps to have an OSNAP or two ready — endpoint, midpoint and perpendicular are the ones you reach for when defining the mirror line against existing geometry. Turn on Object Snap (F3) before you start so you can snap the mirror line precisely to a wall, a centreline or a grid.
Step 2 — Define the mirror line
AutoCAD asks for the 'first point of mirror line' and then the 'second point'. These two points define the axis of reflection. For a vertical mirror, pick a point and then a second point directly above it (turn on Ortho with F8 to lock it vertical). For a horizontal mirror, pick two points along a horizontal line. For a diagonal, snap to the two ends of the angled wall or axis you want to reflect across.
The distance between the two points doesn't matter — only the line they define. So a short vertical drag and a long one give the same mirror, as long as both points sit on the intended axis. Snap to a room centreline to flip a layout into the opposite half perfectly.
Step 3 — Keep or delete the original
After the mirror line, AutoCAD asks 'Erase source objects? [Yes/No]', with No as the default. Press Enter (or type N) to keep the original and create a mirrored copy — the choice for making a symmetrical pair, like two doors flanking a corridor. Type Y to erase the original and keep only the flipped version — the choice when you simply want to reverse the hand of something, such as flipping a door so it swings into the room instead of out.
This single prompt is what makes MIRROR double as both a copy-and-flip and a straight flip. Decide which you need before you answer.
Keeping text readable with MIRRTEXT
Here is the part that catches people. By default, mirroring an object that contains text can flip the text into mirror writing — backwards and unreadable. The behaviour is controlled by the system variable MIRRTEXT.
Set MIRRTEXT to 0 (type MIRRTEXT, Enter, 0, Enter) and text keeps its readable orientation when you mirror — the text moves to the mirrored position but is not reversed. Set MIRRTEXT to 1 and text is reflected like everything else, producing backwards writing. For almost all real work you want MIRRTEXT set to 0. Note that this governs text and mtext; block attributes generally follow sensible orientation rules, but it is still worth checking a mirrored block's labels read correctly before you trust the drawing.
Real uses: opposite hands and symmetry
Mirroring earns its keep on symmetrical and handed layouts. Apartment blocks often repeat a unit and its mirror image either side of a party wall — draw one flat, mirror it across the wall, and the opposite hand is done. Bathrooms and kitchens come in left-hand and right-hand versions; mirror the fitted layout to produce the other hand without re-placing every fixture.
Door and window blocks flip with a quick mirror to change the hinge side or the opening direction. Furniture groups — a sofa and two chairs, a desk and return — mirror to suit a room's orientation. Because a block mirrors as one object, these flips take seconds and stay tidy, with no exploded geometry to clean up afterwards.
Mirror pitfalls to watch for
Three things go wrong most often. First, reversed text, solved by MIRRTEXT 0 as above. Second, a mirror line that isn't quite vertical or horizontal because Ortho was off — the result is a layout tilted by a degree or two. Turn on Ortho (F8) or snap to known points to keep the axis true.
Third, mirroring an asymmetric block and expecting it to stay 'correct'. A door swing is meant to flip; a logo or a directional symbol may not be. Check that the mirrored result still makes sense — a 'NORTH' arrow mirrored sideways now points the wrong way. When in doubt, mirror, then inspect the result before committing the rest of the layout around it.
Free download
Browse the full library — DWG & DXF, no signup.
Questions
Frequently asked
How do I mirror a block without the text going backwards?+
Set the system variable MIRRTEXT to 0 before mirroring. Type MIRRTEXT, press Enter, type 0, press Enter. Now MIRROR moves text to the mirrored position but keeps it readable instead of reflecting it into backwards writing.
What is the keyboard shortcut for the mirror command?+
Type MI and press Enter. That is the command alias for MIRROR. Select the block, define the two points of the mirror line, then choose whether to keep or erase the original.
How do I mirror a block but keep the original too?+
When MIRROR asks 'Erase source objects?', answer No (press Enter, since No is the default). AutoCAD then creates a flipped copy and leaves the original in place — ideal for making a symmetrical pair.
Can I mirror across a diagonal line?+
Yes. The mirror line can run at any angle. Pick the two points of your diagonal axis — snap to the ends of an angled wall, for example — and AutoCAD reflects the block across that diagonal rather than only horizontally or vertically.
Related downloads
Blocks for this guide
Related guides
How-to guide
How to Insert a Tree CAD Block in AutoCAD
Step-by-step guide to inserting a tree CAD block in AutoCAD — download the DWG, set units, use INSERT, scale and place it, then array trees across a site plan.
How-to guide
How to Create a Block in AutoCAD (BLOCK & WBLOCK)
Learn how to create a block in AutoCAD with the BLOCK and WBLOCK commands — pick a base point, choose objects, set units, and save a reusable DWG block library.
How-to guide
How to Array Trees Along a Path in AutoCAD
Use ARRAYPATH to line trees along a road, footpath or curve in AutoCAD — set spacing, align to the path, vary the look, and keep planting on its own layer.