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IntermediateFree AutoCAD course about 22 min

Dimensions and dimension styles

Dimensions tell the builder exactly how big things are. Learn how dimensions are built, how to place them quickly, and how to set up a dimension style that prints correctly at any scale.

In this lesson you will

  • Name the parts of a dimension
  • Place linear, aligned, angular, radial, continued and baseline dimensions
  • Create a dimension style for architectural drawings
  • Keep dimensions associative and on their own layer

Anatomy of a dimension

A dimension is a single associative object made of extension lines, a dimension line, arrowheads or ticks and text. Because it is associative, stretching the wall updates the number automatically — never type over a dimension value to 'fix' it; fix the geometry instead.

A wall with a linear dimension above it. Labels point to the extension lines, the extension-line offset gap from the object, the dimension line, the arrowheads or ticks at each end, and the dimension text reading 3600.3600dimension textdimension lineextensionlineoffset gaptick / arrowmeasured object (wall)
Figure: The parts of a linear dimension. Original KitWren diagram.

Placing dimensions

The DIM command is smart: hover over a line and it previews a linear or aligned dimension; hover over a circle for a radius or diameter; pick two lines for an angle. The specific commands are still useful:

CommandAliasUse
DIMLINEARDLIHorizontal or vertical distance
DIMALIGNEDDALDistance along an angled edge
DIMANGULARDANAngle between two lines
DIMRADIUS / DIMDIAMETERDRA / DDIArcs and circles
DIMCONTINUEDCOA chain of dimensions end-to-end
DIMBASELINEDBASeveral dimensions from one base line

Dimensioning a wall quickly

  1. 1Set the layer A-ANNO-DIMS current.
  2. 2DLI, snap to the outside corner, then the edge of the first opening; place the dimension line 800–1000 mm off the wall (at 1:100).
  3. 3DCO and snap to each subsequent opening edge and wall junction — a continuous chain.
  4. 4Add an overall dimension further out with DLI from corner to corner.
  5. 5Use DIMSPACE to space dimension lines evenly.

Dimension styles

A dimension style (D › DIMSTYLE) controls how dimensions look: tick or arrow, text height, text position, extension line gaps, units and precision. Create one per drawing type rather than overriding individual dimensions.

Typical architectural settings (paper sizes, in mm): Architectural tick 1.5–2 mm, text height 2.5 mm, extension line offset 1–2 mm, extend beyond dimension line 1–2 mm, precision 0.

Tick Annotative in the style. Then the sizes above are paper sizes and AutoCAD scales them for each annotation scale — one style works at 1:50, 1:100 and 1:200. The Annotation lesson explains this in detail.

Good dimensioning practice

  • Dimension to structure and setting-out points builders can measure from.
  • Group dimensions in chains outside the plan; keep them off the drawing where possible.
  • Don't duplicate dimensions or dimension the same thing on two drawings — they will eventually disagree.
  • Give an overall dimension that the chain adds up to.

Quick reference

Command / toolHow to start itWhat it does
DIMType DIMSmart dimension, previews the right type
DIMSTYLEDDimension Style Manager
DIMSPACEType the nameEvenly spaces dimension lines
DIMBREAKType the nameBreaks dimension lines where they cross
DIMREASSOCIATEType the nameRe-attaches dimensions to geometry

Common mistakes

  • Dimension text is tiny or huge on the printed sheet.

    Use an annotative style with paper-size text, and set the correct annotation scale.

  • Typing over a dimension value.

    Never fake dimensions. Change the geometry; the dimension updates.

  • Snapping to dimension endpoints instead of walls.

    Zoom in and use the Endpoint/Intersection snap on the wall itself.

Exercise

Dimension a room

  1. Create an annotative dimension style KW-ARCH with ticks and 2.5 mm text.
  2. Set annotation scale 1:100.
  3. Dimension one external wall with a continuous chain to each opening, plus an overall dimension.
  4. Dimension an angled wall with DIMALIGNED and a curved bay with DIMRADIUS.
  5. Stretch the room 500 longer and watch the dimensions update.

You should end up with: Clear, associative dimensions that update with the geometry.

Checklist

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Lesson quiz

1 / 5

Which command places a chain of dimensions end to end?

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Questions

Should dimensions be in model space or paper space?

Both are used. Dimensioning in model space with annotative styles is the most common approach today and keeps dimensions with the geometry; some offices dimension in paper space through viewports. Follow your office standard.

Free, independent learning material written for KitWren. AutoCAD and AutoCAD LT are registered trademarks of Autodesk, Inc. KitWren is not affiliated with, sponsored or endorsed by Autodesk. We never provide software downloads, licence keys or cracks — use the official sources.