Do CSS Widths Respect Decimal Places?

Decimal Places in CSS Widths: Are They Respected?

The precision of decimal places in CSS widths has been a topic of curiosity for many CSS enthusiasts. This article aims to provide a comprehensive explanation of whether decimal places are taken into account in CSS width declarations.

Percentage Widths: Decimal Places Matter

In the case of percentage widths, decimal places do indeed play a significant role. For instance, if an element is assigned a width of 49.5%, it will take up exactly 49.5% of its containing element's width. This means that fractional percentages, such as 50.5%, can be used to create fine-grained spacing or alignment.

Pixel Widths: Decimal Places Ignored

In contrast, decimal places are not respected for pixel widths. When an element is assigned a pixel width, the browser will round down to the nearest whole pixel. For example, a width of 122.5px will be interpreted as 122px by the browser. This is because pixel values represent specific physical dimensions on the screen, and fractional values are not supported.

Demonstration with an Example

The following code snippet provides a visual demonstration of how decimal places are handled differently in percentage and pixel widths:

#outer {
    width: 200px;
}

#first {
    width: 50%;
    height: 20px;
    background-color: red;
}

#second {
    width: 50.5%;
    height: 20px;
    background-color: green;
}

#third {
    width: 51%;
    height: 20px;
    background-color: blue;
}

<div>

In this example, the outer container has a fixed width of 200px. The three inner elements are assigned widths of 50%, 50.5%, and 51%, respectively. As you can see from the result, the second element, with a width of 50.5%, takes up the correct fractional space within the container.

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