CSS Unit Converter Online

Convert CSS units instantly between px, rem, em, vw, vh, pt, and % with this free online CSS Unit Converter. Simply enter a value in any supported unit, customize the root font size, base font size, or viewport dimensions, and all conversions update automatically in real time.

Whether you're building responsive websites, converting design files into CSS, or creating accessible typography, this tool helps you generate accurate CSS measurements without manual calculations.

Everything runs entirely in your browser for fast, private, and secure conversions.

A CSS Unit Converter is a tool that converts values between different CSS length units used in web development. Since different projects use different units for typography, spacing, layouts, and responsive design, converting between them manually can be time-consuming and error-prone.

This converter automatically translates values between pixels (px), root em (rem), em, viewport width (vw), viewport height (vh), points (pt), and percentages (%) while respecting your custom project settings.

Whether you're converting measurements from Figma, adapting a design system, or migrating a legacy stylesheet, this tool makes CSS unit conversion quick and reliable.

• Convert between px, rem, em, vw, vh, pt, and %
• Live conversion as you type
• Customize root font size
• Set a custom parent font size for em
• Configure viewport width and height
• Accurate responsive unit calculations
• Supports decimal values
• Copy converted values instantly
• Perfect for responsive web design
• Great for typography and spacing
• No registration required — free to use
• Works in all modern browsers, runs entirely in your browser

• Pixels (px)

  Pixels (px) are fixed units representing individual screen pixels. They provide predictable sizing regardless of parent elements and are commonly used for borders, icons, and precise layouts.

  Example:

  font-size: 16px;

  Best for: borders, icons, small UI elements, pixel-perfect layouts.

• Root EM (rem)

  rem is relative to the root (html) font size. If the root font size is 16px, then 1rem equals 16px. Using rem makes typography and spacing more scalable and improves accessibility because users can adjust browser font settings.

  Example:

  font-size: 1.5rem;

  Best for: typography, margins, padding, responsive layouts, design systems.

• EM (em)

  em is relative to the current element's font size (or its nearest parent). Because em scales with its context, it's useful for reusable UI components where child elements should scale proportionally.

  Example:

  padding: 1.25em;

  Best for: component sizing, buttons, nested typography, reusable UI components.

• Viewport Width (vw)

  vw represents a percentage of the browser's viewport width. 1vw = 1% of viewport width, 50vw = half the viewport width.

  Example:

  width: 60vw;

  Best for: responsive layouts, hero sections, fluid typography, full-width containers.

• Viewport Height (vh)

  vh represents a percentage of the viewport height.

  Example:

  height: 100vh;

  Best for: full-screen sections, landing pages, hero banners, mobile layouts.

• Points (pt)

  Points (pt) are primarily used for print stylesheets. 1pt = 1/72 inch. Although pt can be used on screens, px or rem are generally preferred for web interfaces.

  Example:

  font-size: 12pt;

  Best for: print styles, PDF layouts, printable documents.

• Percentage (%)

  Percentage values are relative to another property or parent element, depending on the CSS property being used.

  Example:

  width: 75%;

  Best for: flexible layouts, responsive containers, fluid sizing.

• Enter a numeric value.
• Choose the source CSS unit.
• Set the root font size if using rem.
• Set the parent font size if using em.
• Configure viewport width and height for vw and vh.
• View all converted values instantly.
• Copy any converted unit with one click.

No downloads or registration are required.

Modern web development increasingly favors relative units because they create layouts that adapt better to different devices and user preferences.

Benefits include:

• Better accessibility
• Improved responsive design
• Easier maintenance
• Consistent scaling
• Better support for browser zoom
• Flexible typography
• Cleaner design systems

Using rem for typography and spacing is considered a best practice because it respects the user's preferred font size.

Using relative units like rem and em improves accessibility because text scales according to the user's browser settings.

For the best user experience:

• Prefer rem for font sizes.
• Use % and viewport units for flexible layouts.
• Avoid fixed pixel sizes for body text.
• Test layouts with browser zoom enabled.
• Verify readability on different screen sizes.

These practices help create websites that are easier to use for a wider range of visitors.

All supported units (px, rem, em, vw, vh, pt, and %) are part of the CSS specification and are supported in all modern browsers, including:

• Google Chrome
• Mozilla Firefox
• Microsoft Edge
• Safari
• Opera

Relative units such as rem, em, %, vw, and vh calculate their values based on the current document settings, parent elements, or viewport dimensions.