You edit the dimension style so the text is bigger, click OK, and the drawing does not move. You edit it again, and still nothing. Dimension text size in AutoCAD turns out not to be one setting but three layers stacked on top of each other, and whichever layer wins decides what prints.
This article names all three, and the one command that drags already-drawn dimensions along. For the whole discipline of dimensioning a drawing set, the Institute runs an AutoCAD course for construction.
Two numbers decide the height
The text height on a dimension is the product of two variables:
| Variable | What it does |
|---|---|
DIMTXT | Text height, in drawing units |
DIMSCALE | An overall multiplier for every size on the dimension |
Printed height = DIMTXT × DIMSCALE. Same drawing, same DIMTXT of 2.5:
DIMSCALE | Text height on the model |
|---|---|
| 1 | 2.5 |
| 100 | 250 |
The dimscale variable reaches further than the text. It multiplies arrowheads, extension line offsets, and the gap between stacked dimension lines — everything decorative. Autodesk's page on the DIMSCALE variable describes it as "Sets the overall scale factor applied to dimensioning variables that specify sizes, distances, or offsets", and adds that it "Does not affect measured lengths, coordinates, or angles". The measured figure stays put, because that is the real size of the thing.
Dimension text too small on a 1:100 drawing
This is the most common case by a distance. Construction drawings are drawn in millimetres and plotted at 1:100. You want 2.5 mm text on paper, so you set DIMTXT to 2.5 — and the dimension text too small to see, even zoomed right in.
The reason is arithmetic. That 2.5 is 2.5 millimetres on the model, and the model shrinks a hundredfold when plotted. On paper the text is 0.025 mm tall.
The rule: set DIMSCALE to the inverse of the plot scale.
| Plotted at | DIMSCALE | DIMTXT | Text on paper |
|---|---|---|---|
| 1:100 | 100 | 2.5 | 2.5 mm |
| 1:50 | 50 | 2.5 | 2.5 mm |
| 1:20 | 20 | 2.5 | 2.5 mm |
In the dialog: type D to open the Dimension Style Manager, click Modify, go to the Fit tab, and set Use overall scale of.
Why the old dimensions do not follow
This is where the time goes, and it is not a mistake on your part.
When you change DIMTXT and then draw a dimension, AutoCAD does not write that height into the dimension object. It attaches a dimension style override to it — extended data holding one entry: the group DSTYLE, code 140, value 2.5.
From then on the dimension obeys the override rather than the style. Editing the style does nothing to it:
| What you do | A dimension drawn at DIMTXT 2.5 |
|---|---|
Raise DIMTXT to 5 | still 2.500 |
Raise DIMTXT to 5 and re-save the style | still 2.500 |
Most guides say only that Set Current applies to dimensions drawn afterwards. True, but incomplete: even overwriting the dimension style outright leaves the old ones untouched, because the override lives on the object rather than in the style.
Updating existing dimensions: the command that works
Only one operation strips that override: re-applying the style to the dimension.
By command. Type -DIMSTYLE (with the leading hyphen), choose _Apply, select the dimensions, press Enter.
By ribbon. The Annotate tab, Dimensions panel, the Update button — the same thing.
Measured on three dimensions, the third of which also had its text height set directly to 7:
| Step | dim 1 | dim 2 | dim 3 |
|---|---|---|---|
Drawn at DIMTXT 2.5 | 2.500 | 2.500 | 7.000 |
DIMTXT raised to 5, style re-saved | 2.500 | 2.500 | 7.000 |
After -DIMSTYLE → Apply | 5.000 | 5.000 | 5.000 |
After the last step the extended data is gone entirely — the override is deleted, not masked. Even the dimension with a hand-set height of 7 is pulled back to 5.
That is the thing to watch: Apply removes every override on the selected dimensions, including ones you set deliberately on a few special cases. Select with intent rather than window-selecting the whole drawing.
Changing dimension text height on individual dimensions
When only a few dimensions need fixing and the style should stay put, there are two routes.
First — the Properties palette. Select the dimension, press Ctrl+1, and under Text set Text height. Editing here creates an override on exactly the selected dimensions.
Second — scale the whole dimension. Still in Properties, under Fit, the Dim scale overall box multiplies the whole dimension rather than just the text, so arrowheads and offsets grow with it. Useful when one dimension sits in a viewport at a different scale.
Both routes create overrides. A later Apply wipes them.
That cuts both ways on a drawing you inherited. Before running Apply across a sheet, it is worth knowing which dimensions are carrying overrides and why, because some of them are deliberate: a dimension squeezed into a tight spot with smaller text, or one sitting in a viewport plotted at a different scale. Select a few and compare the Properties values against the style they are assigned to — any difference is an override. Where the drawing came from another office, expect a mixture: dimensions drawn over several years with whatever the variables happened to hold that week. Running Apply over the whole sheet makes them consistent in one step, which is usually what you want, but it is a one-way trip unless you undo immediately.
The text style trap: Properties says one thing, the plot says another
There is one more layer, and it is the quietest of the three.
Every dimension style is tied to a text style. If that text style carries a fixed height other than zero, the style decides what is drawn and DIMTXT is ignored.
Measured on one drawing with DIMTXT left at 2.5:
| Text style of the dimension | Text actually drawn |
|---|---|
| Height 0 | 2.5 |
| Height 3.0 | 3.0 |
The awkward part is elsewhere: in both cases the Properties palette still reports 2.5. You look at the properties, see the number you set, and the plot comes out at a different size.
How to spot it in the dialog: open the Dimension Style Manager, go to the Text tab, and if the Text height box is greyed out, the text style is holding a fixed height. Fix it with STYLE, select that text style, and set Height back to 0.
This is why any text style used for dimensions should carry a height of zero. Setting up text styles is covered in our article on text in AutoCAD.
Setting it once for the whole drawing set
Putting all three layers together into one sequence you run once:
- Type
STYLEand set the height of the dimension text style to 0. - Type
D, click Modify, Text tab, set Text height to the printed height you want, say 2.5. - On the Fit tab set Use overall scale of to the inverse of the plot scale, say 100.
- Click OK, then Set Current.
- Type
-DIMSTYLE, choose_Apply, and select the existing dimensions.
Skip step 5 and the old dimensions stay as they were. Skip step 1 and the two steps after it mean nothing. The current value of the dimtxt variable can be checked at any moment by typing DIMTXT and pressing Enter.
Setting up dimension styles in full is covered in our article on dimension styles in AutoCAD.
Three things often repeated that are not true
| Often repeated | What was measured |
|---|---|
| Edit the style and every dimension follows | One carrying an override does not, even when the style is overwritten |
| Properties shows what will print | A text style fixed at 3.0 draws at 3.0 while Properties reports 2.5 |
DIMSCALE enlarges the measured figure | It scales decoration only; the measurement is unchanged |
Frequently asked questions
Where is dimension text size in AutoCAD set most quickly?
Type D, click Modify, go to the Text tab and set Text height. Then set Use overall scale of on the Fit tab to match your plot scale.
I edited the style but the old dimensions are unchanged.
They carry overrides. Type -DIMSTYLE, choose Apply, and select them.
The Text height box is greyed out.
The text style tied to the dimension style has a fixed height. Type STYLE and set that style's Height back to 0.
What value should DIMSCALE take?
The inverse of the plot scale: 100 for 1:100. With an annotative dimension style, Autodesk notes that DIMSCALE is set to zero automatically and the scale is governed by CANNOSCALE, so leave it alone.
Does running Apply cost anything?
Yes. It deletes every override on the selected dimensions, including deliberate ones. Select with intent.
How can I tell whether a dimension carries an override?
Select it and open Properties: any value differing from its assigned style is an override. After Apply every value matches the style again.