CSS Unit Converter

Convert CSS units

Convert values between CSS units (px, rem, em, %) with customizable base font sizes. Main function - unit conversion table, additional - CSS code conversion with nesting support.

16px(16px)

Base Font Size (16px)

Enter value:

Unit:

Rounding:

Conversion Table

16.0000

rem

1.0000

100.0000

Preset Values Table

Commonly used values, automatically converted based on base font size

px	rem	em	%
4px	0.2500rem	0.2500em	25.0000%
6px	0.3750rem	0.3750em	37.5000%
8px	0.5000rem	0.5000em	50.0000%
10px	0.6250rem	0.6250em	62.5000%
12px	0.7500rem	0.7500em	75.0000%
14px	0.8750rem	0.8750em	87.5000%
16px	1.0000rem	1.0000em	100.0000%
18px	1.1250rem	1.1250em	112.5000%
20px	1.2500rem	1.2500em	125.0000%
24px	1.5000rem	1.5000em	150.0000%
28px	1.7500rem	1.7500em	175.0000%
32px	2.0000rem	2.0000em	200.0000%
36px	2.2500rem	2.2500em	225.0000%
40px	2.5000rem	2.5000em	250.0000%
48px	3.0000rem	3.0000em	300.0000%
56px	3.5000rem	3.5000em	350.0000%
64px	4.0000rem	4.0000em	400.0000%
72px	4.5000rem	4.5000em	450.0000%
80px	5.0000rem	5.0000em	500.0000%
96px	6.0000rem	6.0000em	600.0000%

Online CSS Unit Converter: px, rem, em and % — Complete Guide

In modern web development, adaptability and accessibility of interfaces play a crucial role. Our CSS Unit Converter is a powerful tool for frontend developers and web designers that automates font size and spacing calculations. Forget about calculators and manual formulas: convert px to rem, em, or percentages instantly.

How does the CSS converter work?

The tool works in two modes, covering all layout needs: from converting a single value to processing entire code fragments.

Base Font Size

All relative units (rem, em, %) depend on the base font size. By default in browsers this is 16px, but design systems often use 14px, 18px, or 20px. Our tool allows you to set any base size and saves it in tab settings. You can create separate tabs for different projects and switch between them without losing context.

Instant Conversion (Unit Converter)

Simply enter a value in any field (e.g., in pixels), and the calculator will automatically recalculate it to other units:

PX (Pixels): Absolute unit, precise and predictable.
REM (Root EM): Relative to the root <html> element. The standard for adaptive typography.
EM: Relative to the parent element. Perfect for scalable components.
% (Percentage): Percentage ratio of the base size.

CSS Code Conversion with Nesting Support

A unique feature of our service is the CSS Code Converter mode. Paste your CSS code, select the conversion direction (e.g., from px to rem), and the algorithm will process the entire code. The tool accounts for selector nesting and parent font-size properties to correctly calculate complex em values.

PX vs REM vs EM: What to Choose?

Understanding the difference between units is critically important for quality layout.

Why Use REM Instead of PX?

Using rem allows users to scale the interface through browser settings (e.g., for visually impaired users). If a site is hardcoded in px, changing the font size in the browser won't affect the layout, which degrades accessibility (a11y).

When to Use EM?

The em unit is useful for creating components where spacing (padding, margin) should depend on the element's own font size. However, you need to be careful with em due to the compounding effect. Our converter helps track these dependencies.

Advantages of Our Tool

Multitasking: The tab system allows you to work on multiple projects simultaneously, preserving settings for each.
Progress Saving: All data, including the active tab and rounding settings, is automatically saved in the browser's LocalStorage. You won't lose data when reloading the page.
Flexible Settings: Choose rounding precision (number of decimal places) so your code meets your team's standards.