Conversion Form

EM
IN

About the Unit

EM: EM is a relative unit that depends on the font size of the parent element in which the current element is inserted. That is, 1em will be equivalent to the font size of the parent element. If the font size of the parent element is 20px, 1em will be equal to 20px. This unit is particularly useful when you want to create dynamic layouts that adjust based on the context of the parent element. For example, using em instead of px ensures that the size of fonts, margins, or other layout elements will scale relative to the text size of the parent component, making the design more flexible and responsive. A key detail about em is that it can accumulate when used in chain (i.e., if a child element uses em to set its size and the parent element also uses em, the value will multiply), which can lead to unexpected results if not used carefully.

Pro Tip: emin

Use em for scalable typography and in for print-based measurements.

Quick Reference: Unit Conversion by Tens

EMIN
10em1.666667in
20em3.333333in
30em5in
40em6.666667in
50em8.333333in
60em10in
70em11.666667in
80em13.333333in
90em15in
100em16.666667in
110em18.333333in
120em20in
130em21.666667in
140em23.333333in
150em25in
160em26.666667in
170em28.333333in
180em30in
190em31.666667in
200em33.333333in
210em35in
220em36.666667in
230em38.333333in
240em40in
250em41.666667in

Live Unit Preview

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

10px

10rem

10em

10%

10vw

10vh

Common Mistake

Use em for scalable typography and in for print-based measurements.

Real Code Example

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

Frequently Asked Questions About EM

When should I use em instead of em?

Use em when scaling relative to parent is needed.

How many em is 1em?

Depends on parent font size.

Is em affected by zoom?

Yes, it scales with parent and zoom.

Is em good for fonts?

Yes, especially for nested components.

Keyboard Shortcuts

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

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