Skip to content

Distance Constraints (Distance / Horizontal Distance / Vertical Distance)

In one sentence: Set the straight-line, horizontal, or vertical distance between two points or geometry elements, fixing that measurement as a driving or reference constraint.

Overview

Workbench: Sketcher · Menu: Sketch → Sketcher constraints → Distance / Horizontal Distance / Vertical Distance
Toolbar: Sketcher Constraints · Shortcut: K, D (Distance) · L (Horizontal) · I (Vertical)

Tool Shortcut What it measures
Distance K, D Straight-line distance between two points, or length of a line
Horizontal Distance L Horizontal component (ΔX) between two points, or X-distance from origin
Vertical Distance I Vertical component (ΔY) between two points, or Y-distance from origin

All three support Driving and Reference modes (see Dimension for the deep dive on this topic).

Intuition

Distance is the ruler measurement — the shortest path between two points.

Horizontal Distance is how far apart the points are horizontally, ignoring any vertical offset. Think of a spirit level placed between the points and measuring the horizontal gap.

Vertical Distance is the vertical gap — like a measuring tape hanging straight down between the two heights.

These three tools handle the majority of positional constraints you will apply in everyday sketching. Radius and angle constraints cover the remaining cases.

When to use them

  • Distance: Set the length of a line; set the diagonal distance between two bolt holes; set the clearance between a profile edge and a reference point.
  • Horizontal Distance: Set the width of a feature; set the X-offset of a hole from a reference wall.
  • Vertical Distance: Set the height of a feature; set the Y-offset from a baseline.

When NOT to use them

  • You want the unified tool — use Dimension (D) and press M to cycle to the desired type.
  • You want to fix absolute coordinates (both X and Y at once) — use Lock Position (K, L).
  • You want to constrain a radius or diameter — use Radius/Diameter.

Step-by-step walkthrough

Distance (straight-line)

  1. Select one line (for its length) or two points (for the distance between them).
  2. Press K, D or activate Distance Dimension from the toolbar.
  3. Click to place the dimension label.
  4. Enter the value and click OK.

Horizontal Distance

  1. Select two points or one point (measures from the sketch origin).
  2. Press L.
  3. Enter the horizontal distance (positive = point to the right of the reference; negative = to the left).

Vertical Distance

  1. Select two points or one point.
  2. Press I.
  3. Enter the vertical distance (positive = point above the reference; negative = below).

Tip

When only one point is selected (no second selection), Horizontal Distance and Vertical Distance measure from the sketch origin. This is a quick way to set the absolute X or Y coordinate of a vertex.

Parameters

Parameter Type Default Description
Value Distance (mm) Current measurement The distance to enforce. Can be negative for signed horizontal/vertical measurements.
Mode Driving / Reference Driving See Driving vs Reference.

Horizontal Distance

In depth

Horizontal Distance (DistanceX) constrains the X-coordinate difference between two points. With two points A and B: B.x - A.x = value. With one point and the origin: point.x = value.

Key properties: - Sign matters: a negative value places the second point to the left of the first. - Use it instead of a full Distance constraint when you only need the horizontal component (leaves the vertical component free to be constrained separately).

Vertical Distance

In depth

Vertical Distance (DistanceY) constrains the Y-coordinate difference between two points. With two points: B.y - A.y = value. With one point: point.y = value.

Key properties: - Positive = second point is above the first. - Use it to set the height of a feature relative to a baseline edge.

Common mistakes and pitfalls

Distance between two constrained points is redundant

Cause: Both points were fully fixed by other constraints, so the measured distance is already determined. Adding a Distance constraint on top is redundant.
Fix: Accept the situation (the distance is already set) or redesign the constraints so that the Distance constraint is what fixes one of the points.

Negative horizontal distance produces unexpected result

Cause: You expected DistanceX = 20 to place a point 20 mm to the right, but the order of your selection reversed the sign convention.
Fix: Check which point is the reference and which is the target. If the result is mirrored, change the sign: DistanceX = -20.

Python API

Minimal example

import FreeCAD as App
import Sketcher
import Part

doc = App.activeDocument()
sketch = doc.getObject("Sketch")

idx = sketch.addGeometry(
    Part.LineSegment(App.Vector(5, 3, 0), App.Vector(25, 3, 0)), False)

# Fix the line length (straight distance)
sketch.addConstraint(Sketcher.Constraint("Distance", idx, 20.0))

# Fix start point X coordinate (from origin)
sketch.addConstraint(Sketcher.Constraint("DistanceX", idx, 1, -1, 1, 5.0))

# Fix start point Y coordinate (from origin)
sketch.addConstraint(Sketcher.Constraint("DistanceY", idx, 1, -1, 1, 3.0))

doc.recompute()

Method signatures

# Distance on a single line (its length)
sketch.addConstraint(Sketcher.Constraint("Distance", geoId, value))

# Distance between two points
sketch.addConstraint(Sketcher.Constraint("Distance", geo1, vertex1, geo2, vertex2, value))

# Horizontal distance from point to origin
sketch.addConstraint(Sketcher.Constraint("DistanceX", geoId, vertex, -1, 1, value))

# Vertical distance between two points
sketch.addConstraint(Sketcher.Constraint("DistanceY", geo1, vertex1, geo2, vertex2, value))

See also

  • Dimension — unified constraint tool that auto-detects distance type
  • Radius/Diameter — constrain circle/arc size
  • Angle — constrain the angle between lines
  • Lock Position — set both X and Y at once via the UI