box-sizing property CSS Reference

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Definition and Usage

The box-sizing CSS property is used to alter the default CSS box model used to calculate widths and heights of elements. It is possible to use this property to emulate the behavior of browsers that do not correctly support the CSS box model specification.

• Initial content-box
• Applies to all elements that accept width or height
• Inherited no
• Media visual
• Computed Value as specified
• Animatable no
• Canonical order the unique non-ambiguous order defined by the formal grammar

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Syntax

Formal syntax: content-box | padding-box | border-box

box-sizing: content-box
box-sizing: padding-box
box-sizing: border-box
box-sizing: inherit

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Values

content-box

This is the default style as specified by the CSS standard. The width and height properties are measured including only the content, but not the border, margin, or padding.

padding-box

The width and height properties include the padding size, and do not include the border or margin.

border-box

The width and height properties include the padding and border, but not the margin. This is the box model used by Internet Explorer when the document is in Quirks mode.

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Examples

/* support Firefox, WebKit, Opera and IE8+ */
.example {
  -moz-box-sizing: border-box;
       box-sizing: border-box;
}

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Compatibility

Desktop browsers

Mobile browsers