Understanding Circle Segments, Smooth Geometry, and a Common Limitation in SketchUp
If you’ve ever drawn a circle in SketchUp and wondered why it looks nothing like a circle, you’re not alone. This is one of the most common questions beginners have — and it was exactly the topic of a long-running thread on the official SketchUp Forum.
In SketchUp, circles (and arcs) are not true curves. They are approximations, made of straight line segments. This is why your “circle” looks more like a polygon.
But the good news is:
→ You can control how smooth your circles appear.
→ And understanding how segments work will immediately improve the quality and accuracy of your models.
Let’s break down everything you need to know.
Why Circles Look Blocky in SketchUp
SketchUp uses straight edges to approximate curves. That means:
- A circle is actually a closed loop of line segments.
- By default, SketchUp uses 24 segments.
- With only 24 sides, the result often looks faceted, especially on larger circles or extruded geometry.
This behavior is normal and expected in a polygon-based modeling environment.
How to Make a Circle Smoother: Increase the Number of Segments
There are two main ways to increase the smoothness of a circle.
1. Use the Measurements Box (VCB) While Drawing
Right after selecting the Circle Tool, before you click to complete your circle:
- Type a number (e.g., 48, 96, 120).
- Add the letter s (for “sides”).
- Press Enter.
Example:
96s
This instantly draws your circle with 96 segments instead of 24.
This method is the most reliable and most used.
2. Change Segments in Entity Info (After Drawing the Circle)
If you’ve already drawn the circle:
- Select the circle’s perimeter.
- Open Window → Entity Info.
- You’ll see the current number of segments.
- Type a new number (example: 72).
SketchUp will regenerate the circle with the new segmentation — as long as it hasn’t been edited into something else (e.g., pushed/pulled).
This is extremely useful when you forget to set the number beforehand.
Important Limitation: You Cannot Change the Default Permanently
One of the most frequent questions in the forum thread was:
“The setting persists during the session, but resets to 24 next time I open SketchUp. Can I change the default?”
The answer is:
No — SketchUp always resets circles to 24 sides by default.
This is not user-configurable.
It’s a longstanding behavior, confirmed by SketchUp team members and power users.
It has been requested many times, but still has not been made adjustable.
How Segment Count Affects Modeling
Changing the number of sides affects:
✔ Smoothness
More segments = smoother circles, smoother extrusions, better presentation.
✔ File Size
Higher segmentation means heavier geometry. Large architectural models may slow down.
✔ Accuracy
More segments = more precision for round details (columns, pipes, mechanical parts).
✔ Performance
Using 96–128 segments everywhere in a big model can quickly become overkill.
A practical guideline:
| Type of Circle | Recommended Segments |
|---|---|
| Small details | 24–32 |
| Furniture, props | 48–64 |
| Columns, architecture | 48–96 |
| High-detail mechanical | 96–128 |
Choose your segmentation wisely based on your project.
Expert Tips from the Forum Discussion
1. Decide Segments Before Push/Pull
Once a circle becomes part of other geometry, increasing segments may break faces.
2. Use Components
If you model a single high-detail circle inside a component, copies won’t duplicate the heavy geometry.
3. Use Soften/Smooth Edges
Even with fewer segments, enabling smooth shading can visually hide faceting.
4. Consider Extensions
Some plugins (e.g., FredoTools) generate true arcs and circles with more control.
Links to SketchUp Help Mentioned in the Forum
Here are the official resources referenced in the discussion (rewritten as accessible links):
- Measurements Toolbar Overview
https://help.sketchup.com/article/70071 - Precision Modeling with Tape Measure & Protractor
https://help.sketchup.com/sketchup/measuring-angles-and-distances-model-precisely
These are worth reading if you’re learning precision modeling.
Final Takeaway
SketchUp circles look faceted because they are faceted — they’re made of line segments. But with just a few clicks, you can easily control how smooth they look.
Remember:
- Increase segment count via the Measurements Box or Entity Info.
- Segment settings do not persist between sessions.
- More segments = smoother results, but heavier models.
Mastering this small detail immediately makes your SketchUp models cleaner, more accurate, and more professional.
