Conversion Form

CH
MM

About the Unit

CH: The ch unit is a relative typographic unit based on the width of the '0' character of the current font. This unit is especially useful when you want the width of an element to be proportional to the text content, particularly for input fields or text areas. Using ch ensures that the element size adjusts based on the average character width of the current font, providing precise control over text layout. For example, if you set the width of a text input field to 10ch, it will be wide enough to accommodate 10 '0' characters of the font, making it useful for password fields or numeric inputs. The ch unit is less commonly used than other relative units like em or rem, but it is an excellent choice when precise width based on textual content is needed.

Pro Tip: ch → mm

Ch measures text width, mm is used for print precision.

Quick Reference: Unit Conversion by Tens

CHMM
10ch21.166667mm
20ch42.333333mm
30ch63.5mm
40ch84.666667mm
50ch105.833333mm
60ch127mm
70ch148.166667mm
80ch169.333333mm
90ch190.5mm
100ch211.666667mm
110ch232.833333mm
120ch254mm
130ch275.166667mm
140ch296.333333mm
150ch317.5mm
160ch338.666667mm
170ch359.833333mm
180ch381mm
190ch402.166667mm
200ch423.333333mm
210ch444.5mm
220ch465.666667mm
230ch486.833333mm
240ch508mm
250ch529.166667mm

Live Unit Preview

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

10px

10rem

10em

10%

10vw

10vh

Common Mistake

Be cautious when mixing ch and mm without testing on different screen sizes.

Real Code Example

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