CSS px to rem & rem to px Converter Online Free
rem units scale with the user’s root font size, which is how accessible, zoom-friendly CSS is supposed to work. Enter one or many pixel values and convert them to rem using your own base (16px by default, 10px if your project resets it) — or flip the direction to go rem → px. Batch mode accepts lists like "12 16 24" or full snippets like "padding: 8px 16px;" and rewrites every number for you, with rounding controls so you never ship 0.9375rem when you wanted 0.94rem.
CSS px to rem & rem to px Converter In-Browser Workspace
Input data or select files to begin. 100% private, client-side execution with zero server transmission.
How to Use CSS px to rem & rem to px Converter
- Step 1: Set the root font size your project uses (16px is the browser default).
- Step 2: Choose direction: px → rem or rem → px.
- Step 3: Enter a single value or a space/comma-separated list, or paste a CSS fragment.
- Step 4: Set decimal places (2 is typical for production stylesheets).
- Step 5: Copy the converted values or the rewritten CSS line with one click.
About CSS px to rem & rem to px Converter
A rem (root em) resolves against the html element’s font size, which browsers set to 16px unless changed by the user or a CSS reset. Converting is division: rem = px ÷ root. So 24px with a 16px root is 24 ÷ 16 = 1.5rem; with a 10px project base (common in some component libraries) the same 24px becomes 2.4rem. Reverse conversion multiplies: px = rem × root, giving 1.5 × 16 = 24px. Why bother? Hard-coded pixels ignore a user who bumps default text size for low vision — rem-based spacing and type reflow with that preference and with browser zoom, improving WCAG compliance. Batch parsing tokenizes on whitespace and semicolons, converts every numeric token while leaving units like %, em, vw alone, and preserves property names and separators so "margin: 8px 16px;" becomes "margin: 0.5rem 1.5rem;". Rounding uses toFixed then strips trailing zeros; at two decimals some values are approximations (3px → 0.19rem ≈ 3.04px) which is acceptable for layout but worth knowing for icon pixel-grid work — raise precision or keep px where sub-pixel fidelity matters (borders, shadows). Fractional roots (16.5px) are supported because the math is plain floating point. The tool never touches calc() arithmetic; convert leaf numbers yourself when expressions appear.
Frequently Asked Questions
What root font size should I use?
Browser default is 16px; if your framework sets html { font-size: 10px } use 10 instead so conversions match runtime.
Why does my converted value look slightly off?
Rounding to two decimals introduces tiny error; raise precision or keep px where exact device pixels matter.
Does this convert em units too?
em depends on the parent context, not the root — use rem conversion only when the source unit is px or rem.
Can I paste an entire stylesheet?
Batch mode handles lists and simple declarations; for whole files, run your build tool’s postcss-pxtorem plugin.
Are results computed offline?
Yes — pure arithmetic in your browser; nothing is uploaded.