PX to REM Converter: Real-time CSS Unit Calculator

Instantly convert Pixels to REM (and vice versa). Includes a customizable base size setting and a quick reference table for developers.

PX to REM Converter

Convert CSS units instantly for responsive design

Root Base Size: px
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Quick Reference Table (Base: 16px)

Pixels (px) REM

Why Convert PX to REM?

In modern web development, using REM (Root EM) units instead of fixed PX (Pixels) is a best practice for Accessibility and Responsive Design.

When you define font sizes, padding, or margins in PX, they are fixed. If a user changes their browser's default font size (for visual impairment), your site won't scale. By using REM, your layout respects the user's settings.

How the Calculation Works

The formula is simple but tedious to do mentally repeatedly:
Target PX / Base Font Size = REM Value

By default, most browsers set the root HTML font size to 16px. So, 16px = 1rem, 24px = 1.5rem, and so on. However, some frameworks (like Tailwind CSS) or reset sheets might change this base to 10px or 14px. The GungorKaya.com PX to REM Converter lets you adjust this "Base Size" to match your project perfectly.

Why Use This Tool?

  • Bidirectional: Type in Pixels to get REM, or type in REM to get Pixels.
  • Custom Base: Working on a project with a 62.5% (10px) base? No problem. Just change the base setting.
  • Reference Table: Quickly look up common sizes (12px, 14px, 16px, etc.) without typing anything.

Frequently Asked Questions

What is the formula for PX to REM?
The formula is: Pixels / Base Size = REM. For a standard 16px base, 32px would be 32 / 16 = 2rem.
What is the default base pixel size?
In almost all modern browsers (Chrome, Firefox, Safari), the default root font size is 16px.
Why should I use REM instead of PX?
REM units allow your website to scale based on the user's browser settings. This is crucial for accessibility (visually impaired users who increase default text size) and responsive design.
What is the difference between EM and REM?
REM (Root EM) is relative to the root (html) element. EM is relative to the parent element's font size. REM is generally safer for layout and typography to avoids compounding issues.
Why do developers set font-size to 62.5%?
Setting `html { font-size: 62.5%; }` resets the base size to 10px (since 62.5% of 16px is 10px). This makes math easier: 1.4rem = 14px, 2.0rem = 20px.
Can I use this tool for padding and margins?
Yes. REM units are perfect for spacing (padding/margin) to ensure your whitespace scales proportionally with your text.
Does this converter work with Tailwind CSS?
Yes. Tailwind uses REM by default (e.g., `text-lg` is usually 1.125rem). You can use this tool to calculate custom values for your config file.
How do I convert REM back to PX?
Multiply the REM value by the base size. Example: 2rem * 16px = 32px. Our tool handles this bidirectionally.
Is this tool free?
Yes, the GungorKaya.com PX to REM converter is 100% free and runs locally in your browser.
What about Viewport Units (vw/vh)?
Viewport units are based on the screen size, while REM is based on the font size. They serve different purposes. Use REM for content sizing and VW/VH for layout structure.