Free Px to Rem Converter — Convert Pixels to Rem for Responsive CSS

About Our Free Px to Rem Converter Tool

Modern CSS best practices recommend using rem units instead of px for font sizes, spacing, and layout — making your designs scale correctly with user browser settings and accessibility requirements. Our Px to Rem Converter handles the math instantly. Set your root font size (typically 16px), enter any pixel value, and get the exact rem equivalent.

Key Features

Configurable Base Size — Set any root font size (default 16px)
Bidirectional — Convert px to rem AND rem to px
Bulk Table — See a full conversion reference table
Instant — Results update as you type
Copy-Ready — Output formatted for direct CSS use

How to Use Px to Rem Converter

Set your root font size (usually 16px — the browser default)
Enter your pixel value
Get the rem equivalent instantly (e.g. 24px ÷ 16 = 1.5rem)
Copy the rem value directly into your CSS

Frequently Asked Questions

Why use rem instead of px in CSS?

rem (root em) units scale relative to the document's root font size. When users increase their browser font size for accessibility, rem-based layouts scale correctly while px-based layouts stay fixed, potentially making content unusable for people with visual impairments.

What is the default browser font size?

Most browsers default to 16px as the root font size. This means 1rem = 16px by default. If you change the font-size on the html element (e.g. html { font-size: 62.5%; }), then 1rem = 10px, making conversions simpler.

What is the difference between rem and em?

rem always refers to the root (html) element's font size. em refers to the current element's font size, which compounds when nested — making it harder to predict. rem is generally preferred for predictable, maintainable layouts.

Should I use rem for everything in CSS?

rem is best for font sizes, padding, margin, and layout spacing. For border widths and box shadows, px is usually fine since those typically should not scale with font size. For media query breakpoints, em is often recommended.