PX to REM Converter
Free PX to REM converter with configurable base font size, quick reference table, and bulk conversion for multiple values at once.
About PX to REM Converter
The PX to REM Converter is a free browser-based tool for front-end developers who need to convert between pixel and REM units in CSS. It provides instant, bidirectional conversion with a configurable base font size.
Single Value Conversion
Enter a pixel value to see its REM equivalent, or enter a REM value to see the pixel result. The conversion updates in real time as you type, so there is no need to click a button. The output is formatted as a ready-to-use CSS value that you can copy directly into your stylesheet.
Quick Reference Table
The reference table shows common pixel values (8, 10, 12, 14, 16, 18, 20, 24, 28, 32, 36, 40, 48, and 64) alongside their REM equivalents. This table updates automatically when you change the base font size, giving you a quick lookup for the most frequently used sizes in web design.
Bulk Conversion
Need to convert many values at once? The bulk mode accepts a list of pixel values separated by commas, spaces, or newlines and converts them all simultaneously. This is especially useful when migrating an existing design from pixel-based to REM-based units.
Once you have your REM values, you can clean up your stylesheets with the CSS minifier. All calculations run entirely in your browser with no server involved.
Frequently Asked Questions
What is the difference between PX and REM units?
PX (pixels) are absolute units that stay the same size regardless of any settings. REM units are relative to the root element's font size (the html element). By default, browsers set the root font size to 16px, so 1rem equals 16px. Using REM allows layouts to scale properly when users change their browser font size, improving accessibility.
Why is the default base font size 16px?
All major browsers set the default font size of the html element to 16px. This is the standard baseline that most CSS frameworks and design systems assume. If your project uses a different root font size (for example, 10px for easier math or 62.5% which equals 10px), you can change the base value in this tool to match.
How do I use the bulk conversion mode?
Enter multiple pixel values separated by commas, spaces, or newlines in the bulk input field. The tool converts all values at once and displays each PX value alongside its REM equivalent. This is useful when migrating an existing stylesheet from PX to REM units.
Does changing the base font size affect all conversions?
Yes. Every conversion in the tool - the single converter, the reference table, and the bulk converter - all use the base font size you set. If you change it from 16px to 10px, then 1rem will equal 10px across the entire tool.
Should I always use REM instead of PX?
Not always. REM is recommended for font sizes, padding, margins, and other spacing values because it respects user font size preferences. PX is still appropriate for values that should not scale, such as border widths, box shadows, or very small decorative details. Many developers use a combination of both units depending on the context.