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PX to REM Converter

Convert pixels to rem and em units, and calculate fluid typography CSS clamp() formulas.

Runs in your browser. Nothing you add is uploaded.

What the PX to REM Converter does

Web accessibility guidelines strongly recommend using relative units (REM and EM) instead of static pixels (PX) so typography respects user browser magnification preferences. This tool provides bidirectional conversion between pixels, rems, ems, percentages, and points, alongside an interactive CSS clamp() fluid typography calculator with a live viewport resizer.

How to convert PX to REM and calculate fluid clamp()

  1. Set your root font size base (default is 16px, or switch to 14px, 12px, or 10px).
  2. Enter any pixel or rem value; the other fields update bidirectionally in real time.
  3. In the Fluid Typography section, set your minimum/maximum viewport and font sizes.
  4. Drag the Simulate Viewport slider to watch the responsive text scale smoothly across screen sizes.
  5. Copy the generated clamp() formula or reference the Tailwind CSS font size cheat sheet.

The PX to REM Converter runs entirely in your browser — nothing you enter is uploaded, stored, or logged.

When to use it

Figma to Code Implementation

Quickly convert pixel values from Figma design specifications into accessible rem units for production CSS.

Fluid Responsive Headlines

Use CSS clamp() to make hero titles seamlessly scale from mobile screens (375px) to ultra-wide displays (1440px) without jagged media query breakpoints.

Accessible Theme Development

Audit component libraries to ensure padding, margins, and typography scale appropriately with browser zoom.

Good to know

  • 1rem equals the root html font-size (16px in default browser configurations).
  • CSS clamp(min, preferred, max) eliminates the need for 4 different media queries to resize a single headline.
  • Use REM for font sizes and layout spacing, and PX for 1px borders and hairline dividers.

Frequently asked questions

Why should web developers use REM instead of PX?

REM units scale relative to the root font size set by the user's browser. Using REM ensures your site respects accessibility settings for visually impaired users who increase default font sizes.

How does the CSS clamp() formula work?

The clamp(min, val, max) function sets a value between an allowable minimum and maximum. In fluid typography, 'val' uses a linear slope equation with viewport units (vw) to scale smoothly as the browser window resizes.

What is the difference between REM and EM?

REM (Root EM) is always relative to the root <html> element font size. EM is relative to the font size of the immediate parent element, which can cause compounding size issues when nested.

How does the viewport unit (vw) in clamp() prevent layout shift?

The linear slope formula combines viewport width (vw) with a fixed rem offset, allowing the browser to recalculate font size continuously without triggering layout recalculations.

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