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The flex-grow property is a sub-property of the Flexible Box Layout module.

IT defines the ability for a flex item to grow if necessary. It accepts a unitless value that serves as a proportion. It dictates what amount of the available space inside the flex container the item should take up.

For example, if all items have flex-grow set to 1, every child will set to an equal size inside the container. If you were to give one of the children a value of 2, that child would take up twice as much space as the others.

Syntax

flex-grow: <number>

.flex-item {
  flex-grow: 2;
}

Demo

The following demo shows how the remaining space is being calculated according to the different values of flex-grow

<ul class="flex-container">
  <li class="flex-item">1</li>
  <li class="flex-item">2</li>
  <li class="flex-item">3</li>
  <li class="flex-item">4</li>
</ul>
.flex-container {
  padding: 0;
  margin: 0;
  list-style: none;
  
  -ms-box-orient: horizontal;
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -moz-flex;
  display: -webkit-flex;
  display: flex;
    
  -webkit-justify-content: space-around;
  justify-content: space-around;
  -webkit-flex-flow: row wrap;
  flex-flow: row wrap;
  -webkit-align-items: stretch;
  align-items: stretch;
}

.flex-item:nth-of-type(1) { flex-grow: 1; }
.flex-item:nth-of-type(2) { flex-grow: 1; }
.flex-item:nth-of-type(3) { flex-grow: 2; }
.flex-item:nth-of-type(4) { flex-grow: 1; }
.flex-item:nth-of-type(5) { flex-grow: 1; }

.flex-item {
  
  background: tomato;
  border: 3px solid rgba(0,0,0,.2);
  line-height: 100px;
  color: white;
  font-weight: bold;
  font-size: 2em;
  text-align: center;
}

All items have a flex-grow value of 1 except the 3rd one which has a flex-grow value of 2. It means when the available space is distributed, the 3rd flex-item will have twice as much space as others.

Related Properties

Browser Support

  • (modern) means the recent syntax from the specification (e.g. display: flex;)
  • (hybrid) means an odd unofficial syntax from 2011 (e.g. display: flexbox;)
  • (old) means the old syntax from 2009 (e.g. display: box;)
Chrome Safari Firefox Opera IE Android iOS
21+ (modern)
20- (old)
3.1+ (old) 2-21 (old)
22+ (new)
12.1+ (modern) 10+ (hybrid) 2.1+ (old) 3.2+ (old)

Blackberry browser 10+ supports the new syntax.