How Can You Apply Units to Unitless CSS Variables?

Customizing Unitless CSS Variables with Desired Units

In CSS, the ability to define unitless variables allows for greater flexibility in styling. However, it's common to encounter situations where the variable needs to be used in multiple places with different units, such as percentage for width and pixels for calc() operations.

Introducing calc() and Unit Multiplication

To resolve this, the calc() function can be employed to explicitly add the desired unit to the variable. By multiplying the variable with the appropriate unit coefficient (e.g., 1%), it's possible to achieve the desired behavior.

Example:

Consider a scenario where a CSS variable --mywidth is set to 10. To use it as a percentage for width, simply write:

div {
  width: calc(var(--mywidth) * 1%);
}

This calculation effectively multiplies --mywidth by 1% (0.01), resulting in a width value of 10%.

Extended Use Cases:

Besides percentage, you can use this technique to append any desired unit:

• For pixels: calc(var(--mywidth) * 1px)
• For degrees: calc(var(--mywidth) * 1deg)
• For opacity: calc(var(--mywidth) * 0.1)

Demonstration:

The following snippet illustrates the application of this technique:

:root {
  --a: 50;
}

.box {
  width:calc(var(--a) * 1%);
  border:calc(var(--a) * 0.5px) solid red;
  background:linear-gradient(calc(var(--a) * 0.8deg), blue 50%, green 0);
  padding:20px;
  box-sizing:border-box;
}

In this example, the box element demonstrates the use of --a with different units, including percentage for width, pixels for border, degrees for linear gradient angle, and pixels for padding.

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