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PX to REM Converter: A CSS Units Guide

Learn the difference between px and rem CSS units, when to use each, and convert between them with our free tool.

·Softween

Choosing between px and rem units in CSS is a common decision for front-end developers. Understanding when to use each unit leads to more accessible and maintainable designs.

PX vs REM: What Is the Difference?

  • px (pixels): Absolute unit. 1px is always 1 pixel on screen, regardless of user settings.
  • rem (root em): Relative unit. 1rem equals the font size of the root element (default: 16px).

    • Quick Conversion Table

    PXREM (base 16px)
    10px0.625rem
    12px0.75rem
    14px0.875rem
    16px1rem
    18px1.125rem
    20px1.25rem
    24px1.5rem
    32px2rem
    48px3rem

    The Conversion Formula

    rem = px / base-font-size
px = rem × base-font-size

    With the default base of 16px:

  • 24px = 24 / 16 = 1.5rem
  • 2rem = 2 × 16 = 32px

    • When to Use Each

    Use REM for:

  • Font sizes — respects user browser preferences for accessibility
  • Spacing and layout — scales proportionally with user settings
  • Media queries — responsive breakpoints that adapt to user preferences

    • Use PX for:

  • Borders — 1px borders should stay 1px regardless of settings
  • Box shadows — precise visual effects
  • Fine visual details — where exact pixel control is needed

    • Why REM Matters for Accessibility

    When users change their browser's default font size (common for users with low vision), rem-based layouts scale accordingly. Using px ignores this preference, harming accessibility.

    Try It Yourself

    Convert between px and rem instantly with our free PX to REM Converter. Set any base font size and get accurate conversions.

    Related Tools

    PX ↔ REM Converter

    Convert between PX and REM CSS units with configurable base font size

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