Conversion Form

MM
PERCENTAGE

About the Unit

Millimeter (mm): The millimeter (mm) is a physical unit of measurement, 1/10th of a centimeter. Like cm, mm is commonly used in graphic design and printing, where precise physical measurements are needed. In CSS, mm is useful for defining width, height, and other dimensions of elements in layouts that will be printed or converted to other physical formats. Using mm is an effective way to ensure precise and consistent layout dimensions during the printing process. For digital designs, the mm unit may be less practical, as most web interfaces benefit more from relative units to ensure a more adaptive user experience. However, for technical documents or precision graphics, mm may be the best choice.

Pro Tip: mmpercentage

Use % for responsive layouts and mm for precise print measurements.

Quick Reference: Unit Conversion by Tens

MMPERCENTAGE
10mm39.370079%
20mm78.740157%
30mm118.110236%
40mm157.480315%
50mm196.850394%
60mm236.220472%
70mm275.590551%
80mm314.96063%
90mm354.330709%
100mm393.700787%
110mm433.070866%
120mm472.440945%
130mm511.811024%
140mm551.181102%
150mm590.551181%
160mm629.92126%
170mm669.291339%
180mm708.661417%
190mm748.031496%
200mm787.401575%
210mm826.771654%
220mm866.141732%
230mm905.511811%
240mm944.88189%
250mm984.251969%

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 mm and percentage without testing on different screen sizes.

Real Code Example

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