PX to REM Converter

Convert CSS pixels (PX) to REM units and vice versa with custom root font size setting.

Category: Developer

How to Use PX to REM Converter

Enter the numeric value you wish to convert.
Select conversion direction (PX to REM or REM to PX).
Set your root font size (default: 16px).
Copy your converted value and review the CSS preset scale table.

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Frequently Asked Questions

What is the difference between PX and REM units in CSS?

PX (pixels) are absolute units fixed to screen display dots. REM (Root EM) is a relative unit calculated relative to the root <html> element's font-size. When a user adjusts their browser's accessibility font size, REM units scale proportionally, while PX units remain rigid.

What is the standard root font size used for REM conversions?

The default root font size across all major web browsers (Chrome, Safari, Firefox, Edge) is 16px. Under this default, 1rem = 16px, 0.5rem = 8px, 1.5rem = 24px, and 2rem = 32px.

Can I customize the base root font size (e.g. 10px or 62.5% trick)?

Yes. Many design systems use the '62.5% trick' (setting <html> font-size to 62.5% so 1rem = 10px). You can set the 'Base Root Font Size' input to any value (like 10, 14, or 16) and calculate precise conversions instantly.

Can I convert REM back to PX (REM to PX mode)?

Yes. Select 'REM to PX' from the Conversion Mode dropdown, enter your REM value (e.g., 1.25), and get the exact pixel equivalent based on your configured root font size.

Why does the tool display a common design scale reference table?

The converter includes a responsive reference table showing common UI scale values (4px, 8px, 12px, 16px, 20px, 24px, 32px, 48px, 64px) and their exact REM equivalents for rapid design system reference.