CSS Border Radius Workbench
Generate eight-value elliptical corner CSS, calculate overlap scaling and preview the resulting rounded rectangle locally.
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How to use CSS Border Radius Workbench
Resolve four horizontal and four vertical radii in top-left, top-right, bottom-right, bottom-left order. The CSS overlap rule scales every radius by one common factor when adjoining corners exceed a box side. The preview is generated numerical canvas geometry.
- Enter your own values or load the local synthetic example.
- Run the tool and review the complete result and stated assumptions.
- Copy the output or download the generated file.
Good to know
- Models the outer rounded rectangle only: no visible border, scrollbar, shadow, transform, arbitrary HTML or table painting.
- Box sides1–10000 px, radii up to 100000 px or1000 percent. Preview is scaled to at most 1024×1024 before allocation.
- Horizontal percentages use box width; vertical percentages use box height. A corner with either radius zero is square. No input CSS, HTML or SVG is mounted.
Common questions
Why are the used radii smaller than my inputs?
If adjacent radii exceed any side, CSS applies one common proportional scale to all radii. The report shows that scale and the resulting pixel values.
Is the PNG a screenshot of my website?
No. It is a local canvas preview of the documented simple geometry model.
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