What is the formula for px to em?

em = px ÷ base-font-size. For example, 24px ÷ 16px = 1.5em. The result is relative to the nearest parent element's font size, which is usually the root (html) font size.

What is the default base font size?

Most browsers default to 16px. Unless your CSS sets a different font-size on the or element, 16px is the correct base to use.

What is the difference between em and rem?

em is relative to the nearest parent element's font size, while rem is relative to the root ( ) font size. For consistent sizing, rem is usually easier to reason about; em is useful for components that should scale with their container.

Can I convert em back to px?

Yes. Switch to the "EM to PX" direction in the converter, enter your em value, and the tool calculates px = em × base-font-size.

Why should I use em instead of px?

Em values scale with user browser preferences and parent font size, making designs more accessible and responsive. Fixed px values ignore user text-size settings, which can harm readability for users who need larger text.

PX to EM Converter

Name: PX to EM Converter
Availability: InStock
Author: Nham Vu

Convert CSS px to em (or em to px) instantly with a configurable base font size, batch input, and a handy reference table.

Base Font Size (px)

px — usually 16 (browser default)

Pixel Value

Batch Convert

Enter multiple values separated by spaces or commas.

Common PX → EM Reference

at 16px base

PX	EM	Common use

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Summary

Convert CSS px to em (or em to px) instantly with a configurable base font size, batch input, and a handy reference table.

How it works

Enter the base font size (default 16px — the browser default).
Type a pixel value in the PX input to get the em equivalent, or type an em value to convert back to px.
Use the Batch tab to paste multiple space- or comma-separated px values and convert them all at once.
Copy individual results with the copy button, or copy the full batch output.
Use the reference table to look up common px sizes and their em equivalents.

Use cases

Convert a designer's pixel specs to em units for a scalable CSS stylesheet.
Quickly check what em value corresponds to a target pixel size.
Batch-convert all font sizes in a design token file from px to em.
Verify responsive typography scales using a custom root font size.
Cross-check em values when debugging text that looks too large or small.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu