Conversion Form

REM
IN

About the Unit

REM (Root EM): REM is a relative unit that depends on the root font size, typically defined in the `<html>` element of the document. The main advantage of REM is that it provides a consistent and scalable way to work with measurement units in web design, especially when creating responsive and accessible layouts. When you define the root font size, for example, as 16px, 1rem will be equivalent to 16px. If the root font size is changed, all measurements in rem will adjust proportionally, which makes controlling the layout as a whole easier. This is especially useful for ensuring that the design is consistent and accessible, as users can adjust the font size in the browser. Using rem instead of px helps maintain the layout's proportions when scaling the page globally without needing to adjust each value individually.

Pro Tip: remin

Use rem for responsive typography and in for physical print measurements.

Quick Reference: Unit Conversion by Tens

REMIN
10rem1.666667in
20rem3.333333in
30rem5in
40rem6.666667in
50rem8.333333in
60rem10in
70rem11.666667in
80rem13.333333in
90rem15in
100rem16.666667in
110rem18.333333in
120rem20in
130rem21.666667in
140rem23.333333in
150rem25in
160rem26.666667in
170rem28.333333in
180rem30in
190rem31.666667in
200rem33.333333in
210rem35in
220rem36.666667in
230rem38.333333in
240rem40in
250rem41.666667in

Live Unit Preview

See how different CSS units affect the size of the box below:

10px

10rem

10em

10%

10vw

10vh

Common Mistake

Use rem for responsive typography and in for physical print measurements.

Real Code Example

/* Mobile-first card with rem → in */
.card {
  padding: 0rem;     /* undefinedin */
  font-size: 1.5rem;
  width: min(90vw, 40ch);
}

Frequently Asked Questions About REM

When should I use rem instead of rem?

Use rem for consistent scaling across components.

How many rem is 1rem?

1rem = 16px by default.

Is rem affected by zoom?

Yes, it scales with user settings and zoom.

Is rem good for fonts?

Yes, it's preferred for accessibility.

Keyboard Shortcuts

  • Ctrl + C: Convert
  • Ctrl + I: Invert units
  • Esc: Reset values

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