Free rem ↔ px converter — convert CSS units with any root font size

PXREM
12px0.75rem
14px0.875rem
16px1rem
18px1.125rem
20px1.25rem
24px1.5rem
32px2rem

rem = px ÷ root font size. Calculated entirely in your browser.

📐 REM to PX Converter — Free Online Tool

Convert between rem and px online, free. In CSS, px is an absolute unit while rem is relative to the root (html) font size — by default 16px. This converter turns rem into px and back for any root font size, so you can move between the two units accurately while keeping accessible, scalable layouts (per the W3C CSS Values and Units specification).

🚀 Why use this REM to PX Converter tool?

It converts rem ↔ px against an adjustable root font size, so your spacing and typography stay consistent and accessible. 100% free, no registration, and complete privacy — everything runs locally in your browser, so your data never touches a server.

Key Features

🔁Both directions

Convert rem to px or px to rem instantly, with the math shown so the result is easy to trust.

🎛️Adjustable root

Set the base font size (default 16px) to match your project, including non-default or user-scaled roots.

🔒100% private

Conversion runs locally in your browser; nothing you enter is uploaded or stored.

🆓Free, no signup

Unlimited conversions with no account, on desktop and mobile.

Popular Use Cases

Responsive CSS

  • • Translate a px mockup to rem
  • • Keep accessible scaling
  • • Match a design system's base

Design handoff

  • • Convert Figma px to rem
  • • Spec spacing & type scales
  • • Align dev with design

Refactoring

  • • Migrate px to rem
  • • Audit existing values
  • • Standardize a scale

What It Handles

Units

  • ✓ rem → px
  • ✓ px → rem
  • ✓ Custom root size

Output

  • ✓ Exact value
  • ✓ Shown calculation
  • ✓ Copy result

Workflow

  • ✓ Live as-you-type
  • ✓ No install
  • ✓ Runs offline

Sources & References

Frequently Asked Questions

How do I convert rem to px?

Multiply the rem value by the root font size. At the 16px default, 1.5rem = 1.5 × 16 = 24px. Enter your value and root size and the tool does it instantly, both directions.

What is the default root font size?

Browsers default the root (html) font size to 16px, so 1rem = 16px unless you or the user changes it. This tool defaults to 16 but lets you set any base.

Should I use rem or px?

Prefer rem for font sizes and often spacing, because it scales with the user's browser font-size setting (better accessibility). Use px where you need a fixed value that shouldn't scale, like 1px borders.

Why is rem better for accessibility?

rem respects the user's chosen base font size, so a visitor who increases their browser default sees your whole layout scale proportionally. Fixed px ignores that preference.

Is my input uploaded anywhere?

No. The conversion happens entirely in your browser; nothing you enter leaves your device.

🎓 Pro Tips

  • Tip 1: Avoid setting a px font-size on the html element — it can override the user's browser preference and break rem-based accessibility scaling.
  • Tip 2: Keep a single root size across the project; mixing roots makes rem values inconsistent and hard to reason about.
  • Tip 3: Reference: CSS Values and Units (W3C) defines px and rem — https://www.w3.org/TR/css-values/.