What is the formula for pixels to em?

em = px / base font size. For example, 24px with a 16px base equals 1.5em. The base font size is typically the font-size of the parent element or the root (html) element.

What base font size should I use?

Most browsers default to 16px. Use 16 unless your CSS explicitly sets a different base font size on the html or body element. If you set html { font-size: 18px; }, use 18 as the base.

What is the difference between em and rem?

Em is relative to the font size of the nearest parent element. Rem (root em) is always relative to the root html element's font size. Use rem for consistent global sizing, em for component-level relative scaling.

Why use em instead of px in CSS?

Em units scale with the parent element's font size, so layouts and text adapt when users change their browser font preferences or when you resize a parent. This improves accessibility and responsive design.

Can I convert multiple values at once?

Yes. Enter multiple pixel values in the batch input — one per line or comma-separated — and all will be converted using the same base font size.

Pixels to em Converter

Convert pixel values to CSS em units given a base font size (default 16px).

Convert Pixels to em

Pixel value (px)

Base font size (px) — parent or root element

Browser default is 16px.

Batch Converter

Enter multiple px values — one per line or comma-separated.

Pixel values

Results

px	em	CSS

Copied!

Summary

This tool converts pixel values to CSS em units using the formula: em = px / base font size. The browser default base font size is 16px, but you can set any custom base to match your project. Em units are relative to the parent element's font size, making them useful for scalable, accessible typography and spacing in CSS.

How it works

Enter the pixel value you want to convert.
Set the base font size (default 16px matches the browser default).
The em value is calculated instantly using the formula: em = px / base.
Copy the result or add more values to the batch list.
Use the batch converter to process multiple pixel values at once.

Use cases

Convert a designer's pixel measurements to em for CSS stylesheets.
Ensure scalable typography by expressing font sizes in em units.
Translate fixed px padding and margin values to relative em units.
Build accessible layouts where text scales with user font preferences.
Quickly verify em calculations when reviewing or writing CSS.
Batch-convert a list of pixel values from a design spec to em.

Frequently Asked Questions

Last updated: 2026-07-14 · Reviewed by Nham Vu