QCAD Dimensioning and Annotation: Styles, Tolerances, and Drawing Notes

QCAD Dimensioning and Annotation: Styles, Tolerances, and Drawing Notes

Accurate dimensioning is what separates a sketch from a technical drawing. QCAD provides a full set of dimensioning tools and configurable dimension styles. When a Reddit user on r/FreeCAD asked about using QCAD vs LibreCAD for designing apartment layouts with exact dimensions, multiple commenters pointed out that QCAD's dimensioning and snapping tools are more precise and better organized than LibreCAD's. That matches my experience — QCAD's dimension style system is closer to AutoCAD's in terms of configurability, while LibreCAD's dimensioning is more basic.

One important difference from AutoCAD: QCAD lacks paper space viewports. This means you dimension directly in model space, and your dimension text height must be calculated for the final print scale. This trips up people migrating from AutoCAD who are used to setting text height in paper space and letting viewports handle the scaling. Once you understand this workflow difference, QCAD's dimensioning is quite capable.

This guide covers everything from basic linear dimensions to tolerance display and annotation best practices, based on real production drawing experience.

Dimension Types

Linear Dimensions

• Horizontal: Measures horizontal distance between two points
• Vertical: Measures vertical distance
• Aligned: Measures actual distance along the line direction
• Rotated: Measures at a specified angle

Angular Dimensions

Measures the angle between two lines or three points.

Radial Dimensions

• Radius: Measures circle/arc radius with R prefix
• Diameter: Measures circle/arc diameter with Ø prefix

Other Types

• Leader: Points to a feature with text annotation
• Ordinate: Measures X or Y coordinate from a datum

Creating Dimensions

Linear Dimension

1. Select Dimension > Linear from the menu or tool matrix
2. Click the first extension line origin
3. Click the second extension line origin
4. Click to position the dimension line

Aligned Dimension

1. Select Dimension > Aligned
2. Click first point
3. Click second point
4. Click to position the dimension

Angular Dimension

1. Select Dimension > Angular
2. Click the first line
3. Click the second line
4. Click to position the angle text

Radius/Diameter

1. Select Dimension > Radius or Diameter
2. Click the circle or arc
3. Click to position the dimension text

Leader

1. Select Dimension > Leader
2. Click the start point (arrow end)
3. Click intermediate points for the leader path
4. Press Enter, then enter the text

Dimension Style Configuration

Creating a Dimension Style

1. Dimension > Dimension Settings
2. Configure the following:

General

• Text height: 2.5mm (standard for most drawings)
• Text font: Select from available fonts
• Arrow size: 2.5mm
• Arrow type: Architectural tick, closed arrow, or open arrow
• Extension line offset: 1mm (gap from origin)
• Extension line extension: 2mm (beyond dimension line)
• Dimension line gap: 0.625mm (text offset from line)

Precision

• Linear precision: 0.0 (one decimal place) or 0.00 (two places)
• Angular precision: 0.0°
• Tolerance precision: 0.00

Units

• Linear unit format: Decimal
• Angular unit format: Decimal Degrees
• Measurement scale: 1.0

Tolerances

• Mode: None, Symmetric (±), Deviation (upper/lower)
• Upper value: e.g., 0.1
• Lower value: e.g., 0.1
• Tolerance text height: 1.8mm (smaller than main text)

Saving Dimension Styles

QCAD stores dimension settings per drawing. To reuse settings:

1. Configure dimensions in a template drawing
2. Save as a .dxf template file
3. Start new drawings from this template

Tolerance Display

Symmetric Tolerance (±)

For dimensions with equal upper and lower tolerances (e.g., 50±0.1):

1. Dimension Settings > Tolerances > Mode: Symmetric
2. Set value: 0.1
3. Result: 50 ±0.1

Deviation Tolerance

For asymmetric tolerances (e.g., 50 +0.2/-0.1):

1. Dimension Settings > Tolerances > Mode: Deviation
2. Upper value: 0.2
3. Lower value: 0.1
4. Result: 50 +0.2 / -0.1

Limits Tolerance

For showing actual limits instead of nominal ± tolerance:

1. Dimension Settings > Tolerances > Mode: Limits
2. Upper value: 50.2
3. Lower value: 49.9
4. Result: 50.2 / 49.9

Text Annotations

Single-Line Text

1. Draw > Text > Text (Single Line)
2. Click insertion point
3. Enter text
4. Set height and angle

Multi-Line Text

1. Draw > Text > Text (Multi Line)
2. Click first corner, then opposite corner to define text box
3. Enter text in the editor
4. Set font, height, alignment

Text Styles

QCAD supports multiple text styles:

1. Edit > Application Preferences > Text
2. Configure default font, height, and width factor
3. For per-entity text properties, use the Property editor

Annotation Best Practices

1. Dimension on dedicated layers — create A-ANNO-DIMS and A-ANNO-NOTE layers
2. Use consistent text heights — 2.5mm for dimensions, 3.5mm for notes, 5mm for titles
3. Avoid overlapping dimensions — use MOVE to adjust dimension positions
4. Use leaders sparingly — too many leaders clutter the drawing
5. Dimension to object snaps — always snap to endpoints or centers for accuracy
6. Check dimension accuracy — use INFO > Distance to verify critical dimensions

Printing Dimensions at Correct Scale

Since QCAD lacks paper space viewports, dimension text must be sized for the final print scale:

• For 1:50 scale: text height in drawing = 2.5mm × 50 = 125mm
• For 1:100 scale: text height = 2.5mm × 100 = 250mm

Set the text height in Dimension Settings to match your print scale.

Dimension Style Templates for Different Industries

Different industries have different dimensioning standards, and QCAD's dimension style system can accommodate most of them. For mechanical engineering drawings following ASME Y14.5, you'll want to set arrow size to 3mm, text height to 2.5mm, and tolerance display to limits with two decimal places. For architectural drawings, arrowheads should be architectural ticks rather than filled arrows, text height should be 2.5mm at the final print scale, and dimensions should display to the nearest millimeter or fractional inch. For electrical schematics, dimensions are less critical but leader lines for component labels need consistent spacing and text alignment. The key is creating a template file for each industry standard you work with, pre-configured with the correct dimension settings. Save these templates in a shared folder so all team members use the same standards. When starting a new project, open the appropriate template and immediately save it with the project name — this ensures every drawing starts with correct dimension styles.

Conclusion

QCAD's dimensioning tools cover all standard dimension types with configurable styles, tolerance display, and text annotations. The key to professional output is consistency — use a template with pre-configured dimension settings and always dimension to object snaps for accuracy. The main workflow difference from AutoCAD is the lack of paper space viewports, which means you must calculate text height for the intended print scale manually. This is a limitation but also a simplification — there's no viewport scale confusion to deal with. For users coming from LibreCAD, QCAD's dimension style system will feel more capable and closer to professional CAD standards. With proper template setup and consistent practices, QCAD produces dimensioned drawings that meet professional standards for mechanical, architectural, and electrical documentation.