PX to REM Converter
100% LocalConvert px to rem, em, pt and vw with configurable root size.
Enter a pixel value and your root font size. Converts to rem, em, pt, and vw simultaneously.
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What is PX to REM Converter?
Frequently Asked Questions
Technical Deep Dive
PX to REM Converter
Convert pixel values to rem, em, pt, and viewport-relative (vw) units with a configurable root font size (default 16px). Includes a batch converter for pasting multiple values at once, and a Tailwind CSS spacing scale reference table.
Two-Way Conversion
Convert in either direction with consistent semantics on the round-trip.
Accessibility-First
REM-based units respect user font size preferences, making your designs WCAG-compliant by default.
Production-Sized
Built to handle real-world payloads, not just textbook examples.
01 Unit Comparison Matrix
| Unit | Basis | Primary Use Case | Responsive Profile |
|---|---|---|---|
| PX | Fixed Dots | Borders, Divider Lines | None |
| REM | Root (HTML) | Typography, Spacing | Global Scale |
| EM | Parent Element | Component Padding | Local Context |
| VW / VH | Viewport Size | Hero Sections, Modals | Fluid Scaling |
| CH | Character Width | Max Line Width | Typography Context |
02 Transformation Pipeline
03 Why REM Matters for Accessibility
WCAG 2.2 Success Criterion 1.4.4 requires that text can be resized up to 200% without loss of content or functionality. When you use pixel-based font sizes, browsers cannot scale your text in response to the user's preferred font size setting. REM-based sizing inherits from the root element, which browsers control, ensuring your typography automatically respects accessibility preferences.
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Browser Font Size Settings Approximately 3% of users change their browser's default font size from 16px to a larger value (typically 18-24px) for readability. PX-based layouts break for these users; REM-based layouts scale gracefully. This is legally actionable under ADA and EAA regulations.
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The 62.5% Technique Setting
html { font-size: 62.5%; }makes 1rem = 10px, simplifying mental math (16px = 1.6rem). However, this technique can cause issues with third-party components that assume 16px base. The modern approach is to keep 16px base and use this converter for the math. -
When PX Is Still Correct Use pixels for values that should NOT scale with font size: border widths (1px borders should stay 1px), box-shadow offsets, and decorative hairline dividers. A 1px border becoming 2px when the user increases font size looks wrong and wastes visual space.
04 Common Reference Values
| PX | REM (16px base) | Tailwind Class | Typical Use |
|---|---|---|---|
| 4px | 0.25rem | p-1 | Micro spacing, icon gap |
| 8px | 0.5rem | p-2 | Inline padding |
| 12px | 0.75rem | text-xs | Caption text |
| 14px | 0.875rem | text-sm | Secondary text |
| 16px | 1rem | text-base | Body text (default) |
| 20px | 1.25rem | text-xl | Subheadings |
| 24px | 1.5rem | text-2xl | Section headings |
| 32px | 2rem | text-3xl / p-8 | Page titles |
| 48px | 3rem | text-4xl | Hero text |
| 64px | 4rem | p-16 | Section spacing |
05 Related Tools
CSS unit conversion is part of a broader responsive design workflow. These tools handle adjacent concerns.
CSS Unit Converter
Full-spectrum CSS unit conversion including ch, ex, and container query units.
Type Scale Generator
Generate a modular type scale with harmonious font size ratios for your design system.
Spacing Scale Generator
Create a consistent spacing scale using your base REM value and a ratio multiplier.