CSS Units Converter

Convert between px, rem, em, vw, and vh.

Reference Values

Understanding CSS Units

Choosing the right CSS unit is crucial for creating **responsive and accessible websites**. Each unit has a unique relationship to the page, and understanding their differences can save you from layout headaches.

  • **px (Pixels):** An absolute unit. It's fixed and does not scale, making it simple but not ideal for responsive layouts.
  • **rem (Root Em):** A relative unit that is based on the font size of the **root element** (<html>). This makes it great for responsive typography, as changing one value at the root affects the entire page.
  • **em (Element Em):** A relative unit based on the font size of its **parent element**. This can make it difficult to manage, as its value can change based on the nesting level of elements. For this tool, we assume it is relative to the root font size, which is a common approach for simplicity.
  • **vw/vh (Viewport Width/Height):** Relative units based on the dimensions of the **browser's viewport**. 1vw is 1% of the viewport width, and 1vh is 1% of the viewport height. They are excellent for creating elements that scale proportionally to the screen size.

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