What's the difference between EM and REM units in CSS?

EM units are relative to their parent element's font size, while REM units are relative to the root element's font size. REM provides more predictable scaling since it's not affected by parent element font sizes, making it ideal for consistent typography systems.

Why should I use viewport units (vh, vw) instead of percentages?

Viewport units are relative to the browser viewport dimensions, not the parent container. This makes them perfect for full-height sections, responsive typography, and layouts that need to adapt to the actual screen size rather than container size.

What's the standard conversion rate between pixels and REM?

With the default 16px root font size, 1rem = 16px. So 24px = 1.5rem, 32px = 2rem, 48px = 3rem, etc. This ratio changes if you modify the root font size in your CSS using html { font-size: XXpx; }.

When should I use physical units (cm, mm, in) in CSS?

Physical units are primarily used in print stylesheets where you need precise physical measurements. They're less common in screen stylesheets since different devices have different pixel densities, making px, em, and rem more reliable for digital displays.

How do viewport units work with mobile browsers?

Viewport units work reliably across all modern browsers and devices. Mobile browsers handle vh/vw units correctly, though you should test for edge cases like landscape/portrait orientation changes and browser UI elements that might affect the viewport size.

What's the difference between vmin and vmax?

VMIN uses the smaller viewport dimension (width or height), while VMAX uses the larger dimension. VMIN is great for responsive elements that should never exceed the smaller screen edge, while VMAX is useful for elements that should scale with the larger available space.

CSS Units Converter

Convert between any CSS length units with precision including px, em, rem, vh, vw, %, cm, mm, in, pt, and pc units. Perfect for responsive design and cross-browser compatibility with real-time preview and calculation history.

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Common pixel values for quick conversion

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Enter a value and choose the units to convert between

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Value in Pixels

How it works: Converts CSS unit values using standard conversion ratios. Absolute units (px, pt, pc, cm, mm, in) use fixed ratios. Relative units (rem, em, %) require a base font size or container width context — defaults to 16px for rem/em and 100% for percentage.

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Convert between all CSS units instantly. Transform pixels to REM, EM, viewport units, percentages, and print units for responsive design and cross-device compatibility.

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