Professional CSS Unit Converter with Batch Processing and CSS Code Block Support
A powerful tool for converting between pixels (px) and rem units in CSS. Features batch conversion, CSS file import with drag-and-drop, CSS code block processing, conversion history, and keyboard shortcuts for efficient workflow.
The PX to REM Converter tool helps you convert between pixels and rem units for responsive web design. REM units are relative to the root element's font size, making them ideal for scalable, accessible designs.
What is REM? REM (Root EM) is a CSS unit that is relative to the font size of the root element (html). If the root font size is 16px, then 1rem = 16px, 2rem = 32px, and so on. This makes REM ideal for creating scalable, accessible layouts.
The main converter allows you to convert individual values between pixels and rem units.
Switch between PX to REM and REM to PX modes using the toggle button. The converter adapts to show the active input field with enhanced visibility.
By default, conversion happens automatically as you type. Disable auto-convert to manually trigger conversion with the Convert button or Ctrl+Enter.
rem = px / baseFontSize
Example: 32px / 16px = 2rem
px = rem × baseFontSize
Example: 2rem × 16px = 32px
The batch conversion feature allows you to convert multiple values at once. This is especially useful when migrating existing CSS from pixels to rem units. The tool now supports both simple value lists and full CSS code blocks with automatic detection.
The tool automatically detects the input format and applies the appropriate conversion method:
16px 1.5rem 24px 2remEach line is converted individually. The tool detects px or rem units automatically.
{.container {{\n margin: 16px 32px;\n padding: 8px 12px;\n font-size: 14px;\n}}}CSS code is detected automatically (presence of braces, colons, semicolons, or common CSS properties). All px values are converted to rem while preserving the CSS structure.
Tip: Batch conversion is perfect for converting entire CSS files. Copy your pixel values or CSS rules, paste them here, convert, then copy the results back to your stylesheet. The tool automatically detects whether you're using simple values or CSS code blocks.
New Feature: CSS Code Block Support! The batch converter now intelligently detects CSS code and converts all px values to rem while preserving your CSS structure, including complex selectors, nested rules, and shorthand properties.
The tool automatically saves your recent conversions, storing up to 20 entries. This feature allows you to revisit and reuse previous conversions.
Switch to the "History" tab to see all your recent conversions with timestamps and base font size settings.
Click any history item to restore those values and settings. The converter will revert to the base font size used for that conversion.
Export your conversion history as a JSON file for documentation or to share with team members.
Remove all history entries with the Clear button. This action cannot be undone.
The base font size is the foundation for all REM calculations. By default, it's set to 16px (the browser default), but you can customize it to match your project's root font size.
Browser default, most common for web projects
Easy calculation: 1rem = 10px
Often used for larger, readable typography
Alternative for accessibility-focused designs
Important: Match the base font size in this tool to the root font size defined in your CSS (usually on the `html` element). This ensures accurate conversions that work with your design system.
Quickly switch between common framework base font sizes using the preset buttons in the converter panel. This feature saves time when working with different CSS frameworks and design systems.
Default Bootstrap framework font size
Tailwind's default root font size
Ant Design component library default
MUI default typography settings
Simplified: 1rem = 10px for easy mental math
Enhanced readability for accessibility
Pro Tip: The preset buttons use a responsive grid layout that adapts to different screen sizes. On mobile devices, the grid automatically switches to 2 columns for better touch interaction.
The PX to REM Converter now includes adjustable decimal precision, allowing you to control the number of decimal places in conversion results (from 2 to 5 decimal places). This feature is particularly useful when you need specific precision levels for different projects or design systems.
Select your desired precision level (2-5 decimal places) in the converter panel. Higher precision provides more accurate conversions but may result in longer decimal values.
Speed up your workflow with these keyboard shortcuts:
| Shortcut | Action |
|---|---|
| Ctrl + Enter | Convert the current value |
| Ctrl + C | Copy the converted result |
| Ctrl + R | Reset both input fields |
Note: On Mac, use Cmd instead of Ctrl.
Common pixel to rem conversions at the default 16px base font size. Click any value to use it in the converter.
Convert legacy pixel-based CSS to modern REM units for better scalability and accessibility. Use batch conversion to process entire stylesheets.
REM units scale naturally with user preferences and browser settings, making your designs more accessible across different devices and font size settings.
Establish consistent spacing and sizing in your design system by converting design specs (often in pixels) to REM units.
REM units respect the user's root font size preferences, ensuring your designs remain usable for users who need larger text.
Build reusable components with relative sizing. Changes to the root font size will propagate throughout your components automatically.
Convert design measurements to developer-friendly REM values, ensuring accurate implementation in code.
The CSS Code Output Panel generates ready-to-use CSS snippets using your converted values, saving you time when implementing designs in your projects.
When converting 24px to REM (base 16px), the panel generates:
font-size: 1.5rem;
margin: 1.5rem;
padding: 1.5rem;
width: 1.5rem;When converting 2rem to PX (base 16px), the panel generates:
font-size: 32px;
margin: 32px;
padding: 32px;
width: 32px;Tip: The CSS Code Output Panel updates automatically when you perform conversions, so you always have the latest snippets ready to use.
The CSS Property Converter allows you to paste entire CSS rules or complete CSS blocks and automatically convert all pixel values to rem units. This is especially useful when migrating existing stylesheets or working with design specs that use pixel values.
margin: 16px 32px; and convert all px values to rem in one step.container {
margin: 16px 32px;
padding: 8px 12px;
font-size: 14px;
border-radius: 4px;
}.container {
margin: 1rem 2rem;
padding: 0.5rem 0.75rem;
font-size: 0.875rem;
border-radius: 0.25rem;
}Tip: You can paste entire CSS files or specific rules. The converter will find all px values and convert them appropriately. This is perfect for migrating legacy CSS codebases to modern rem-based units.
margin: 16px 32px 8px 24px; → margin: 1rem 2rem 0.5rem 1.5rem;
box-shadow: 2px 4px 8px rgba(0,0,0,0.5); → box-shadow: 0.125rem 0.25rem 0.5rem rgba(0,0,0,0.5);
width: calc(100% - 16px); → width: calc(100% - 1rem);
The CSS File Import feature allows you to drag and drop entire CSS files directly into the converter. The tool will automatically read the file and convert all px values to rem units. This is perfect for migrating entire stylesheets without manual copy-pasting.
Simply drag a CSS file from your file explorer and drop it into the CSS input area. The converter will highlight to indicate it's ready to receive the file. Once dropped, the file is read and converted automatically.
For mobile devices or when drag-and-drop isn't convenient, click the "Choose file" link or button to open the file picker. Select a CSS file and it will be loaded and converted automatically.
Note: The file import feature only accepts .css files for security and compatibility. Other file types will be rejected with an error message. Files are processed locally in your browser - no data is uploaded to any server.
Pro Tip: Use the CSS File Import feature to quickly convert entire stylesheets during a migration project. You can drop multiple files one after another, and each will be converted independently. Combine this with the batch conversion for mixed input formats.