Scale and mirror
SCALE resizes objects about a base point; MIRROR flips them across a line. Together they save hours on symmetrical buildings and on drawings that arrive at the wrong size.
In this lesson you will
- Scale objects by a factor
- Scale to a known length with Reference
- Mirror objects and keep text readable
- Know when not to scale
SCALE
Remember: you draw full size, so you should almost never scale building geometry to make it fit a sheet. SCALE is for fixing wrong units, resizing symbols, and design changes.
- 1Type
SC, select objects, Enter. - 2Pick a base point — the point that stays still.
- 3Type a factor:
2doubles,0.5halves,1000converts metres to millimetres.
Scaling by reference
When you know what length something should be but not the factor — for example a scanned plan traced at the wrong size — use the Reference option: R, pick two points on a dimension you know (the current length), then type the correct length. AutoCAD works out the factor.
MIRROR
Mirroring half a symmetrical building, then mirroring its dimensions and furniture, halves the drawing work.
- 1Type
MI, select objects, Enter. - 2Pick two points on the mirror line (snap to the building's centreline; turn on Ortho).
- 3Answer Erase source objects? —
Nkeeps the original (a symmetrical copy),Yflips it.
Keeping text readable
The MIRRTEXT system variable controls text: 0 (the default) keeps mirrored text reading left to right; 1 mirrors it back-to-front. Leave it at 0. Blocks with text will still flip — check door tags and furniture labels after mirroring.
Quick reference
| Command / tool | How to start it | What it does |
|---|---|---|
| SCALE | SC | Resizes about a base point |
| MIRROR | MI | Flips across a mirror line |
| MIRRTEXT | System variable | 0 = text stays readable when mirrored |
Common mistakes
Scaling the whole plan to fit the paper.
Undo. Set the scale in the layout viewport instead.
Mirrored doors swing the wrong way for the design.
Mirror is exact — check handed items (doors, stairs) after mirroring.
Exercise
Semi-detached pair
- Draw one half of a pair of houses: an 8000 × 10 000 outline with an internal wall and a door swing.
- Mirror it across the party wall line, keeping the original.
- Draw a 1000 line, then scale it by reference so it becomes 2400.
- Scale a circle by 0.5 from its centre.
You should end up with: A symmetrical pair drawn once.
Checklist
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Lesson quiz
Which SCALE factor converts metres to millimetres?
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