What CSS units does this converter support?

It supports all major CSS units: px (pixels), rem (root em), em (parent em), vh (viewport height), vw (viewport width), % (percentage), pt (points), cm (centimeters), and mm (millimeters).

Why do rem and em conversions need a base font size?

rem is relative to the root element's font size (usually 16px by default), and em is relative to the parent element's font size. Setting the correct base values gives you accurate pixel equivalents for your specific design context.

How are viewport units (vh/vw) calculated?

1vh = 1% of the viewport height, and 1vw = 1% of the viewport width. You can set your target viewport dimensions in the context settings to get accurate px conversions for responsive design.

When should I use rem instead of px?

Use rem for font sizes and spacing so your layout scales with the user's browser font settings, improving accessibility. px is fine for borders, shadows, or elements that shouldn't scale.

Yes, completely free. All conversions happen in your browser instantly — no server calls needed.

CSS Units Converter

Convert between CSS units: px, rem, em, vh, vw, %, pt, cm, mm. Adjust base font size and viewport for accurate results.

Value

From Unit

Context Settings

Base Font Size (rem base)

Parent Font Size (em base)

Viewport Height (vh base)

Viewport Width (vw base)

Conversions

rem

2.0833

1.5625

100.00

12.000

0.4233

4.2333

Relative units (rem, em, vh, vw, %) depend on context. Adjust the settings above for accurate results.

How to Use

Convert between CSS units: px, rem, em, vh, vw, %, pt, cm, mm. Adjust base font size and viewport for accurate results.

1Enter a numeric value in the 'Value' field.
2Select the source unit (e.g., px) from the 'From Unit' dropdown.
3All equivalent values in other CSS units appear instantly.
4Expand 'Context Settings' to set your base font size and viewport dimensions for accurate rem/em/vh/vw conversions.
5Click 'Copy' next to any result to copy it to your clipboard.

Key Features

Converts between px, rem, em, vh, vw, %, pt, cm, mm
Adjustable base font size, parent font size, and viewport dimensions
Instant real-time conversion as you type
One-click copy for each converted value
No server needed — all calculations run in your browser

Frequently Asked Questions

Learn More

CSS Units Explained: px, rem, em, vh, vw and When to Use Each