How to dimension in Revit starts with one difference from 2D drafting: the number is not typed, it is read from the model. Move a wall and the number follows; type a new number into the dimension and the wall moves by exactly that much.
This article covers the dimensions, spot elevations and slopes of Chapter 14 of the Institute's textbook Autodesk Revit 2027 for Architectural Documentation, ordered the way you work, with screenshots from Revit 2027 in English. Text and tags have their own article, how to tag in Revit, and 2D detailing is in filled regions and 2D details. To learn the documentation stage in full, see the Revit Architecture course.
Step 1 — Aligned dimensions and snap points
Almost every annotation command lives on the Annotate tab.
| Panel | Meaning |
|---|---|
| Dimension | Nine dimension tools; the last three are spot elevation, spot coordinate and spot slope |
| Detail | Detail lines, regions, detail components, revision clouds, detail groups, insulation |
| Text | Text, spell check, find and replace |
| Tag | Tags for each category |
| Tool | Meaning |
|---|---|
| Aligned | Parallel to the element. The most used, shortcut DI |
| Linear | Horizontal or vertical regardless of the element's angle |
| Angular | Angle between two lines |
| Radial, Diameter | Radius and diameter of arcs |
| Arc Length | Length of an arc |
| Spot Elevation | Spot elevation, see Step 4 |
| Spot Coordinate | Coordinates, for site plans |
| Spot Slope | Slope, see Step 5 |
Autodesk covers these tools in Dimensions.
Placing a dimension string: click each point in turn, then click in empty space to place the line. The hard part is hitting the right thing: hover over a wall and press Tab to cycle snap points, and the status bar tells you what is highlighted.
| Snap | Meaning |
|---|---|
| Wall faces | Wall faces. Vietnamese drawings dimension rooms to the faces |
| Wall centerlines | Wall centreline. Use it for grid strings |
| Center of core | Core centreline, ignoring finish layers |
| Faces of core | Core faces |
Vietnamese architectural drawings usually carry three strings outside the building:
Tip. Use Wall centerlines for the grid string and Wall faces for the inner string. Mixing snap types within one string is the quickest way to a wrong drawing, because the string no longer adds up to the overall.
Step 2 — edit dimensions: move elements and lock dimensions
Use a dimension to move an element. Select a wall and its dimensions turn blue; type a new value and the wall moves by exactly that much. It is more precise than dragging, and the standard way to resize a room after modelling, with no redrawing.
Lock a dimension. Click the padlock on a dimension and the two elements keep their distance: move one and the other follows. Lock too much and, when the scheme changes, Revit refuses to move things because of constraints, and you have to hunt for every padlock.
Note. Lock only relationships that never change, such as the depth of a window reveal or a door's distance from a corner. Never lock room sizes, since those change most.
Step 3 — a dimension style for Vietnamese drawings
The Metric template's dimension style looks odd to Vietnamese readers. Select a dimension, click Edit Type, click Duplicate and name the copy before changing anything.
| No. | Element | Meaning |
|---|---|---|
| 1 | Top of Graphics | Dimension String Type is Continuous. Leader Type, Leader Tick Mark and Show Leader When Text Moves control leaders when text is dragged away. Tick Mark is Diagonal 1mm, the slash Vietnamese drawings also use |
| 2 | Witness lines | Witness Line Gap to Element 1.5 mm is the gap to the element; Witness Line Extension 1.5 mm runs past the dimension line |
Two rows outside the boxes matter too: Line Weight is the pen number, default 1; set Centerline Symbol to None if you do not want Revit to draw a centreline symbol.
| No. | Element | Meaning |
|---|---|---|
| 1 | Text group | Text Font is Trebuchet MS. Read Convention Up, then Left sets the reading direction of rotated dimensions |
| 2 | Primary Units | Units Format opens the units dialog; Dimension Prefix and Dimension Suffix add text around the value |
| 3 | Other group | Equality Text is EQ, shown when spaces are equal. Change it if your drawings use another mark |
Click Units Format to open the Format dialog.
| No. | Element | Meaning |
|---|---|---|
| 1 | Units | Millimeters: the unit printed on the drawing, independent of project units |
| 2 | Rounding | 0 decimal places, rounded to the millimetre as Vietnamese drawings expect |
Use project settings at the top: on, the style follows Project Units; off, it keeps its own units. Turning it off lets one drawing carry two dimension units.
Tip. Build two styles into the office template: one for 1:100 plans, one with smaller text for 1:20 details. Name them by scale so nobody has to think.
Step 4 — spot elevations with Spot Elevation
Floor levels, wet-area levels, wall tops and roof levels are placed with Spot Elevation. Select one and click Edit Type.
| No. | Element | Meaning |
|---|---|---|
| 1 | Elevation Base | Where the value is measured from. Project Base Point measures from the project origin, matching your levels; Survey Point from the survey benchmark; Relative from the current view's level |
| No. | Element | Meaning |
|---|---|---|
| 1 | Primary Units | Units Format sets units and decimals. Elevation Indicator adds text before or after the value; Elevation Indicator as Prefix/Suffix picks which |
Vietnamese drawings give levels in metres to three decimals with a sign: +3.600, -0.030. Set that up in four steps:
- Duplicate the Spot Elevation type and name it for your drawings, such as
CAO-DO-VN. - Open Units Format, set Units to Meters and Rounding to 3 decimal places.
- In the same dialog, tick Show + for positive values so Revit adds the plus sign.
- Set Text Location to Above Leader if you want the text above the leader.
Note. Spot elevation units are separate from dimension units, so one drawing can show dimensions in mm and levels in m out of the box. Autodesk explains this in Spot Dimensions.
Step 5 — slopes with Spot Slope
Spot Slope reads the slope straight from an element's face, so it cannot disagree with the model. It takes two clicks, following the status bar prompts:
- Click to specify measurement point: in an elevation or section, hover over a sloped edge until Revit highlights it and previews the value, then click once.
- Click to select offset side: click again on the side where the text should go.
Beginners often click once, press Esc, see nothing and think the tool is broken. It was waiting for the second click.
While the tool runs, the Graphics panel has two boxes: Slope Representation picks the symbol, default Arrow; Offset from Reference sets the distance from the edge, default 1.5 mm. After the first click Slope Representation greys out, so choose it first.
| No. | Element | Meaning |
|---|---|---|
| 1 | [No Slope] | Revit reads the model correctly: the roof slab is flat, so there is no slope to report. This is the right result, not an error |
| 2 | Text i=2% | The fall written as text with an arrow, the quick way for small areas |
| 3 | Tag M2 | The roof build-up code, looked up in the build-up legend |
| Approach | When to use it |
|---|---|
| Text and arrow | Quick and clear enough for bathrooms, balconies and small roofs where the screed is left to the contractor |
| Real slopes in the model | Large roofs, many drains, water paths to check. Slower, but Spot Slope reads real values and updates with the roof; see how to create a roof in Revit |
Tip. Run Spot Slope over roofs, balconies and terraces to see where the model has real falls and where there is only text. To show percentages, go to Manage › Project Units, row Slope, and choose Percentage; every slope annotation in the file follows.
Try it: plan dimensions and section levels
Plan (Exercise 25, steps 1–7), on a model with walls, doors and rooms.
- Open plan 1F. Duplicate the dimension style and name it
KT-1-100. Open Units Format and check Units is Millimeters with 0 decimals. - Dimension the inner string along the top edge of the building: each opening and wall segment. Use Wall faces.
- Dimension the grid string outside it, using Wall centerlines.
- Add the overall string outermost. Check the three strings agree.
- Select an interior wall and type a new value into its dimension to move it 200. Watch, then undo.
- Duplicate the spot elevation type as
CAO-DO-VN. Set Units to Meters, 3 decimals, and tick Show + for positive values. - Place spot elevations on the living room floor and the bathroom floor. Note both values.
Section (Exercise 26, steps 1–3).
- Open section
MC-A-Aand set the scale to 1:50. - Dimension the storey height, door height and railing height.
- Place spot elevations at every key level: floor, door head, beam soffit, roof.
Common dimensioning problems
| Problem | Cause and fix |
|---|---|
| String does not add up to the overall | Mixed snap types in one string. Delete and redo with one snap type |
| Wall will not move, constraint warning | A locked dimension. Find the padlock on the related dimensions and unlock it |
| Spot Slope shows nothing | You clicked once and pressed Esc. The tool needs a second click for the text side |
| Slope shows [No Slope] | The face is flat in the model. Model the fall or write it as text |
| Levels show mm instead of m | The spot elevation type's Units Format is not set to Meters |
Frequently asked questions
How to dimension in Revit quickly?
Type DI for Aligned, hover over a wall and press Tab to choose the snap, click each point, then click in empty space. Use one snap type per string.
Why are levels in metres while dimensions stay in mm?
The spot elevation type has its own Units Format. Set Meters, 3 decimals and Show + for positive values.
Should I lock dimensions?
Only fixed relationships, such as a window reveal. Locking room sizes creates constraint conflicts when the design changes.
Related articles
- How to tag in Revit and add text — text, Vietnamese fonts, tags and parameters
- Revit filled regions and 2D details — detail lines, legends, drafting views
- How to create a roof in Revit — real falls that Spot Slope can read
- How to export Revit drawings to CAD and PDF — dimensions and text in 2D output