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REM to PX Converter

Convert between REM and pixels (PX) for responsive web design. Set your base font size and convert individual values or entire CSS stylesheets instantly.

The root font size (typically 16px in most browsers)
Enter single values, CSS properties, or entire stylesheets

📋 Quick Reference Table:

💡 Quick Guide:

  • REM Units: Relative to the root element's font size (typically 16px)
  • Batch Conversion: Paste entire CSS blocks to convert all values at once
  • Custom Base Size: Adjust the base font size if your project uses a different root size
  • Flexible Input: Works with or without unit labels (1.5 or 1.5rem)

About REM to PX Converter

Our free online REM to PX converter makes it easy to convert between REM and pixel values for responsive web design. Whether you're converting individual values or entire CSS stylesheets, this tool provides instant, accurate conversions with customizable base font sizes.

Key Features

  • Bidirectional Conversion: Convert REM to PX and PX to REM in one tool
  • Custom Base Size: Set your project's root font size for accurate conversions
  • Batch Conversion: Convert entire CSS blocks or stylesheets at once
  • Flexible Input: Accepts values with or without unit labels
  • CSS Property Support: Preserves CSS syntax when converting properties
  • Quick Reference Table: Dynamic conversion table for common values
  • Swap Function: Quickly reverse input and output for testing
  • Copy to Clipboard: One-click copy for easy use

How to Use This Converter

  1. Select Mode: Click "REM to PX" or "PX to REM" button
  2. Set Base Size: Enter your root font size (default is 16px)
  3. Enter Values: Type or paste REM/PX values or CSS code
  4. Convert: Click the "Convert" button to see the result
  5. Copy or Swap: Copy the result or swap for reverse conversion

Understanding REM vs PX

PX (Pixels) are absolute units that represent a fixed size on screen. A value of 16px will always be 16 pixels regardless of user settings or screen size. While precise, pixels don't scale with user preferences.

REM (Root Em) units are relative to the root element's font size. If the root font size is 16px, then 1rem = 16px, 2rem = 32px, etc. REM units scale with user preferences and are essential for accessible, responsive design.

The Conversion Formula: PX = REM × Base Font Size. For example, with a 16px base: 1.5rem × 16px = 24px. Conversely, 24px ÷ 16px = 1.5rem.

Why Use REM Units?

  • Accessibility: REM units respect user font size preferences in browser settings
  • Consistency: All REM values scale proportionally when base size changes
  • Responsive Design: Easier to create layouts that adapt to different screen sizes
  • Maintenance: Change one root font size to scale entire design
  • Modern Standard: Industry best practice for scalable, accessible web design

Common Use Cases

  • Design Handoffs: Convert designer's pixel specs to REM for implementation
  • Legacy Code: Modernize old PX-based CSS to responsive REM units
  • Documentation: Provide both REM and PX values for developer reference
  • Testing: Verify calculations and check how designs scale
  • Learning: Understand the relationship between REM and PX units
  • Prototyping: Quickly experiment with different base font sizes

Base Font Size Guide

16px (Default): The standard browser default. Most websites use this as the baseline.

14px: Sometimes used for compact interfaces or data-heavy applications.

18px or 20px: Increasingly popular for better readability, especially for content-focused sites.

Custom Sizes: Some design systems use non-standard base sizes like 10px for easier mental math (1rem = 10px, 1.6rem = 16px).

Best Practices

  • Use REM for font sizes, spacing, and layout dimensions
  • Use PX for small details like borders (1px, 2px) or fixed-size elements
  • Never set font-size on the html element in pixels - use percentage or leave default
  • Consider using EM for component-level spacing that should scale with local font size
  • Document your base font size in your CSS or design system
  • Test designs with different user font size settings

Conversion Examples

Example 1 (REM to PX): With 16px base, 1.5rem converts to:
Result: 24px (1.5 × 16 = 24)

Example 2 (PX to REM): With 16px base, 32px converts to:
Result: 2rem (32 ÷ 16 = 2)

Example 3 (CSS Property): margin: 2rem 1.5rem; converts to:
Result: margin: 32px 24px;

Example 4 (Batch Conversion): Paste multiple CSS properties and convert all REM values at once while preserving formatting.

Tips for Using This Tool

  • Use the quick reference table to see common conversions at a glance
  • Adjust base size to match your project's root font size setting
  • Paste entire CSS blocks for batch conversion of all values
  • The tool preserves CSS syntax and property names
  • Values without units are accepted (e.g., "1.5" instead of "1.5rem")
  • Use Swap function to quickly test round-trip conversions

REM vs EM vs PX Comparison

REM: Relative to root element. Consistent across all components. Best for global spacing and typography.

EM: Relative to parent element. Compounds with nesting. Best for component-specific scaling.

PX: Absolute unit. Precise but not scalable. Best for borders, shadows, and fixed elements.

Privacy and Security

All conversions are performed entirely in your web browser using JavaScript. No CSS code or values are sent to any server, ensuring your work remains completely private and secure.