ToolZeno

CSS Border Radius Generator

Design, customize, preview, and export modern CSS border-radius values with four independent corner controls, elliptical slash syntax, live interactive drag handles, preset galleries, Tailwind classes, SCSS, JSON export, and shareable URLs.

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Mastering Modern CSS Border Radii for User Interface Design

Rounded corners are a cornerstone of modern web application design. From gentle 8px radii on dashboard cards to organic fluid blobs and sleek iOS squircle app icons, the CSS border-radius property transforms rigid rectangular HTML boxes into approachable, polished UI elements.

ToolZeno's production-grade CSS Border Radius Generator enables web developers and UI designers to visually craft, fine-tune, preview, and export standard or complex elliptical corner curves instantly in the browser.

Anatomy of the CSS border-radius Syntax

The border-radius shorthand can take anywhere from 1 to 8 distinct values depending on complexity:

// Single value (All 4 corners equal):
border-radius: 16px;
// Four independent corners (TL TR BR BL):
border-radius: 40px 10px 50px 20px;
// Elliptical syntax (Horizontal / Vertical):
border-radius: 40px 10px 50px 20px / 20px 60px 10px 40px;

Clockwise Order

When 4 values are declared, CSS evaluates corners starting from Top-Left, proceeding clockwise to Top-Right, Bottom-Right, and Bottom-Left.

Horizontal & Vertical Radii

Using the slash / separator defines separate X-axis and Y-axis curvature radii, forming smooth ellipses instead of uniform quarter-circles.

Percentage Units (%)

Percentages calculate corner radii based on the element's physical bounding box (width for X-axis, height for Y-axis). 50% forms circles or pills.

Relative Units (rem / em)

Using rem or em ensures border radii scale gracefully alongside typographic text sizes for responsive interfaces.

Crafting Pills, Circles, and Fluid Blobs

Depending on your design requirements, corner curves fulfill different user experience roles:

  • Pills & Capsules: Using border-radius: 9999px guarantees full height rounding on action buttons regardless of width changes.
  • Circular Avatars: Applying border-radius: 50% on square containers creates pixel-perfect circular profile pictures and status badges.
  • Organic Blobs: Combining asymmetrical elliptical percentages (e.g. 60% 40% 30% 70% / 60% 30% 70% 40%) creates dynamic fluid graphic shapes for modern landing page backgrounds.

Best Practices for Responsive Border Radii

Nested elements (such as an image inside a card container) should maintain proportional corner radii. To prevent unnatural gaps, set the inner element's radius equal to the outer radius minus the container padding thickness.

Frequently Asked Questions

The CSS border-radius property allows web developers to round the outer border corners of any HTML element. It can accept a single radius for all corners, four individual corner values, or separate horizontal and vertical radii to create elliptical shapes.

When specifying four values in CSS border-radius (e.g., border-radius: 40px 10px 50px 20px;), they are applied in clockwise order starting from the top-left: 1st value = Top-Left, 2nd value = Top-Right, 3rd value = Bottom-Right, 4th value = Bottom-Left.

An elliptical border radius defines different radii for the horizontal (X-axis) and vertical (Y-axis) curves of a corner. The values before the slash '/' set the horizontal radii, while values after the slash set the vertical radii (e.g., border-radius: 40px 10px 50px 20px / 20px 60px 10px 40px;).

To create a perfect circle, set border-radius to 50% on an element with equal width and height. To create a pill or capsule shape on rectangular buttons, set border-radius to 9999px or 50% height.

No. ToolZeno's CSS Border Radius Generator runs 100% client-side inside your browser using JavaScript. No design data, parameters, or color choices leave your local device.

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