CSS Units Converter

Convert between px, rem, em, vw/vh/vmin/vmax, %, ch/ex, and print units using real context values. See a multi-unit table instantly.

ValueNumber to convert

FromTo

Swap from/to units instantly.

Root font size (rem)Usually 16pxElement font size (em)Matches element context% context size (px)% of what? Set the contextViewport width (px)e.g., 1440Viewport height (px)e.g., 900DPI (print units)CSS default is 96

Use current viewport

ch width ratio (em)Approx. width of “0” in emex height ratio (em)Approx. x-height in emPrecision (digits)

Tip: Set % context and DPI for print units; ch/ex are font-dependent approximations.

Explain mode

Result

16 px = 1 rem

Root: 16px · Element: 16px · % context: 100px · DPI: 96

Viewport: 1440px × 900px · ch: 0.5em · ex: 0.5em

Reverse: 1 rem = 16 px

Multi-output

px16

rem1

em1

vw1.1111

vh1.7778

vmin1.7778

vmax1.1111

Design tokens mode

Paste tokens and convert to rem or Tailwind-style spacing.

Output

Tokens inputSupports px/rem/em values. ch/ex are font-dependent approximations; use in the main converter.

Output previewNo tokens yet

Paste tokens to see converted output.

Clamp helper

Generate a responsive clamp() expression quickly.

Preferred

Min (px)Preferred (px)Max (px)

Output

clamp(16px, 24px, 40px)

How to use

Enter a value and choose from/to units.
Set root font size for rem and element font size for em; adjust viewport and context inputs.
Review the multi-output table for key units at once.

Examples

16px → 1rem (root font 16px)
24px → 1.5rem (root font 16px)
8px → 0.5rem (root font 16px)

FAQ & privacy

Does this run locally? Yes. All calculations happen in your browser.

Which units are supported? px, rem, em, vw, vh, vmin, vmax, %, ch, ex, pt, pc, in, cm, mm.

What’s the difference between rem and em? rem uses the root font size; em uses the element font size.

How should I set % context? Use the size the percentage is based on (container width/height).

Are ch/ex exact? They are font-dependent; adjust ratios for your font.

How do vw/vh work? Values are based on the viewport width/height you set (default 1440×900).

Why no fr? Grid fractions need layout context, so they belong in a dedicated grid tool.