CSS Unit Converter

About This Tool

This tool converts CSS length units among px, em, and vw to support precise typography and responsive layouts for web projects. It targets frontend developers, UI engineers, and design teams working on web interfaces.
Context values such as root font size and viewport width are optional but recommended to reflect real CSS conditions.
Conversions rely on standard CSS semantics: 1em equals the root font size in pixels, and 1vw equals 1 percent of the current viewport width. The calculator computes an intermediate px value when needed and then converts to the target unit, ensuring consistent results across unit pairs.
Examples include converting 16px to em with a root font size of 16px (1em), or translating 50px to vw at a 1024px viewport (approximately 4.88vw). This tool outputs a single numeric value with the target unit, suitable for direct use in CSS declarations. It is particularly helpful for scaling typography, margins, and paddings across breakpoints while maintaining proportional relationships.
By providing both the source context and target unit, users can rapidly compare alternatives, maintain visual rhythm, and reduce iterative testing. The approach emphasizes fidelity to CSS unit semantics and practical applicability in design systems and responsive layouts.

Sign in to see all your usage