To create a radius in SketchUp, you'll primarily use the Arc tools for rounded corners and curved edges, the Circle tool for circular shapes, or combine the Follow Me tool with an arc profile for advanced filleting. The key to achieving an exact radius lies in utilizing SketchUp's Measurements box for precise input.
Master the Arc Tools for Rounded Corners and Curves
The Arc tools are fundamental for introducing curves and rounding sharp corners in your SketchUp models, allowing you to define a specific radius with ease.
The Arc Tool (A)
This is the most common and direct method for drawing arcs and creating specific radius rounded corners. When aiming for a precise measurement, such as a one-foot radius on a corner, this tool is your primary choice.
- Select the Arc Tool: Find it in the Large Tool Set or by pressing A on your keyboard.
- Define First Endpoint: Click once to set the starting point of your arc.
- Define Second Endpoint: Move your cursor along an edge or to another point and click again to set the end point of your arc. For rounding a corner, these two points should be equidistant from the corner's vertex.
- Define the Bulge/Radius: Move your cursor outwards from the line formed by your two endpoints. As you move, SketchUp displays the arc's radius in the Measurements box.
- Enter Exact Radius: To make an exact radius rounded corner, simply type the desired radius (e.g.,
1'for one foot,20cm, or0.5m) into the Measurements box and press Enter before clicking the third time. This ensures your corner gets that specific radius, like a "nice one foot radius" mentioned in various modeling contexts. - Complete the Arc: Click a third time to finalize the arc, or simply press Enter after typing the radius.
- Practical Tip: To round a sharp corner, use the Tape Measure tool (T) to create guide points at the desired radius distance from the corner along both edges. Then, use these guide points as your arc's first and second endpoints.
The Two Point Arc Tool
This tool is useful when you have two distinct points for your arc's span and want to control the curve's bulge or radius from there.
- Select the Two Point Arc Tool.
- First Point: Click to define the first endpoint of your arc.
- Second Point: Click to define the second endpoint.
- Define Bulge/Radius: Move your cursor to define the curve's bulge. You can type a specific bulge distance or radius into the Measurements box and press Enter.
The 3 Point Arc Tool
Use this tool when you need to define an arc by three points that it must pass through, which is less direct for radius input but excellent for specific geometric constraints.
- Select the 3 Point Arc Tool.
- First Point: Click to define the starting point.
- Second Point: Click to define a point on the arc.
- Third Point: Click to define the arc's endpoint.
Using the Circle Tool for Radial Shapes
The Circle Tool (C) is perfect for creating full circular faces or for defining the base of objects that inherently have a radius, such as cylinders or spherical forms.
- Select the Circle Tool: Find it in the Large Tool Set or press C.
- Define Center Point: Click once to set the center of your circle.
- Define Radius: Move your cursor outwards. SketchUp will show the radius in the Measurements box.
- Enter Exact Radius: Type your desired radius (e.g.,
50cm,2') and press Enter to create a circle with that precise radius. - You can then use the Push/Pull tool (P) to extrude this circle into a cylinder.
Advanced Radii: Filleting Edges with the Follow Me Tool
For creating continuous rounded edges or "fillets" (like a quarter-round molding along a counter), the Follow Me Tool combined with an arc profile offers powerful capabilities. This is especially useful for applying a consistent radius along an entire path.
- Draw the Path: Sketch the edges or lines that you want to round. This will be the path along which your radius profile will be swept.
- Create the Radius Profile: On a plane perpendicular to the start of your path, draw a small arc (e.g., a quarter circle) using the Arc tool. The radius of this arc will be the radius of your rounded edge. Ensure the arc's endpoints touch the path.
- Select the Path: Use the Select tool (Spacebar) to select the entire path you drew in step 1.
- Activate Follow Me: Select the Follow Me Tool.
- Click the Profile: Click on the arc profile you created in step 2. SketchUp will sweep the arc along the selected path, creating a smooth, rounded edge with the exact radius defined by your profile arc.
Quick Reference: SketchUp Radius Tools
| Tool Name | Icon | Primary Use Case | Key for Exact Radius |
|---|---|---|---|
| Arc |  |
Rounded corners, single curves | Type [radius] then Enter after 2nd click |
| Two Point Arc |  |
Arcs defined by two endpoints and a bulge | Type [bulge_distance] or [radius] then Enter |
| 3 Point Arc |  |
Arcs passing through three specific points | Less direct radius control; focused on point definition |
| Circle |  |
Full circular faces, bases for radial extrusions | Type [radius] then Enter after center point click |
| Follow Me (with Arc profile) |  |
Fillets, complex rounded edges along a path | Radius defined by the profile arc's dimensions |
Enhancing Precision and Workflow
Achieving accuracy with radii in SketchUp is crucial for professional results.
- Use the Measurements Box: This is your best friend for precision. After activating a tool (like Arc or Circle), type the exact dimension (radius, length, segment count) into the Measurements box in the bottom right corner of your SketchUp window and press Enter. This guarantees an exact radius.
- Leverage Inference: SketchUp's powerful inference engine helps you align points, edges, and axes. Watch for the colored inference lines (red, green, blue for axes; magenta for parallel/perpendicular) to snap to precise locations.
- Construction Lines (Tape Measure Tool): Use the Tape Measure tool (T) to draw temporary guide lines at precise distances. These guides are invaluable for accurately placing the endpoints of your arcs or the center of your circles.
- Components and Groups: To prevent new geometry from sticking to existing parts of your model, always group (G) or componentize elements, especially when adding radii to complex shapes. This isolates your work and makes editing easier.
- Plugins/Extensions: For highly complex or multiple filleting and chamfering operations, consider exploring extensions from the SketchUp Extension Warehouse, such as "RoundCorner" by Fredo6. These tools can automate the process of rounding numerous edges simultaneously with precise radii.
