The Secret to Perfect Rounded Corners

In the world of design, the little details make all the difference. One of those details that separates a good design from a great one is how you handle rounded corners on elements that are nested inside each other, like a thumbnail image inside a padded card. It’s easy to just guess and set a smaller `border-radius` on the inner element, but this often leads to a subtle but noticeable visual hiccup where the curves aren't perfectly parallel. It's like a race car track where the inner and outer lanes don't have the same smooth curve—it just feels a bit clumsy.

The secret to achieving that professional, polished look is to use a little bit of math. To make the curves perfectly parallel, the inner element's corner radius needs to be precisely calculated based on the outer element's radius and the space (the padding and any borders) between them. This calculator is designed to do this one job perfectly. It takes all the guesswork out of the process. You just tell it your design's dimensions, and it instantly gives you the mathematically correct `border-radius` for your inner element. It's a simple tool that helps you achieve a high level of precision and quality in your designs, ensuring your interfaces feel clean, consistent, and professionally crafted every single time.

How to Use the Calculator

This tool is designed to be as simple as possible while giving you immediate visual feedback on your design:

1. Set the Outer Radius: Start by entering the `border-radius` value (in pixels) that you're using for your main, outer container or card.
2. Set the Padding: Enter the `padding` value (in pixels) that creates the space between your outer container and the inner element.
3. Set the Border Width: If your outer container has a border, enter its width here. If it doesn't have a border, just set this to 0.
4. See the Result Instantly: The calculator will immediately update the "Live Preview" to show you exactly how the elements look with the perfectly calculated inner radius. It will also generate the precise CSS code you need in the box below.

You can then click the "Copy" button to grab the generated CSS and paste it directly into your project's stylesheet.

Tips for Perfect Rounded Corners

• Consistency is Everything: Use this calculator to create a consistent and professional look across all your website's components that use nested rounded corners, like user profile cards, product displays, or image galleries. This creates a subtle but powerful sense of quality.
• Borders are Part of the Padding: A common mistake is to forget that an element's border takes up space. This calculator correctly accounts for that. If you have an outer element with `padding: 20px;` and `border: 2px solid;`, the total space between the outer curve and the inner curve is 22px. This tool handles that math for you.
• It's a Detail That Matters: This might seem like a small thing, but getting it right is a hallmark of high-quality front-end development and UI design. It shows a level of care and precision that users can *feel*, even if they can't consciously point it out. It's what makes a design feel solid and well-crafted.