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px ↔ rem Converter

Developer Tools

Root font-size based conversion with common scale table

Quick Answer

px ↔ rem Converter: Root font-size based conversion with common scale table. rem = px ÷ root font-size (browser default 16px).

px
px
rem
24px = 1.5rem · 1.5rem = 24px
1 rem16 px
24 px1.5 rem
1.5 rem24 px
62.5% trick10px = 1rem

Calculation steps

  1. 1rem = px ÷ root font-size. 24px ÷ 16 = 1.5000 rem.
  2. 2px = rem × root font-size. 1.5rem × 16 = 24.00 px.
  3. 3html { font-size: 62.5% } makes root 10px, so 1.6rem = 16px — mental math becomes trivial.

Common scale (click to fill)

pxremUsage
12px0.75remCaption text
14px0.875remSmall body
16px1remDefault body (browser base)
18px1.125remLarge body
20px1.25remSmall heading
24px1.5remH3 heading
32px2remH2 heading
48px3remH1 display
rem respects user browser font settings (accessibility); px does not. Use rem for font-size and layout spacing, px for borders (1px hairline) and box-shadow. em is relative to PARENT font-size — compounds dangerously in nested elements.

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How to Use

  1. Paste or type content: drop code/text into the px ↔ rem Converter or fill the parameters.
  2. Choose mode/options: switch format, rules or processing as needed.
  3. Live output: results appear instantly — nothing is submitted, data stays in your browser.
  4. One-click copy: copy the output straight into your development environment.

Key Points

  • px ↔ rem Converter is a free online developer tool — open and use, no sign-up.
  • All calculations run locally in your browser; your data never leaves the device.
  • Key capability: Root font-size based conversion with common scale table.
  • Results come with formulas and reference tables so you can verify every number.

Formula & How It Works

px ↔ rem conversion

rem = px ÷ root font-size (browser default 16px)
em is relative to the parent (compounds); rem is always root-relative
vw = px ÷ viewport width × 100
Trick: set html font-size to 62.5% so 1rem = 10px

Example: 24px at 16px root = 1.5rem; 24px on a 1440px viewport ≈ 1.667vw.

FAQ

How do I use the px ↔ rem Converter?
Open the page and fill in the input fields — results update automatically. Root font-size based conversion with common scale table.
Are the results accurate?
Yes. Standard formulas and conversion factors are used and verified.
Is it free? Do I need to sign up?
Completely free. No registration, login or download required.
Does it work on mobile?
Yes. The responsive design works on phones, tablets and desktops.
Is my data saved?
No. Everything runs locally in your browser.

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Source & Updates

Based on RFC 4648, ECMA-262 and related specifications. Last updated: 2025-07

Last updated:

Formulas and content on this page are reviewed by the YiJianSuan team. For reference only — official sources prevail.

Maintained and periodically reviewed by the YiJianSuan editorial team — review process in ourEditorial Policy.

Cite this page: YiJianSuan. px ↔ rem Converter[EB/OL]. https://www.yijiansuan.com/en/c/dev/px-rem

Results provided by this tool are for reference only and do not constitute professional advice.