How to display 3 items per row in flexbox?

Flex container:

• You probably want to use display: flex not inline-flex.
• Add flex-wrap: wrap to allow wrapping onto multiple lines.
• Remove width: 33% if you wish it to take entire space avaiable.

For 3 items per row, add on the flex items:

• flex-basis: 33.333333%
• You can also use the flex‘s shorthand like the following: flex: 0 0 33.333333% => which also means flex-basis: 33.333333%.

.serv ul {
  display: flex;
  flex-wrap: wrap;
  padding-left: 0;
}

.serv ul li {
  list-style: none;
  flex: 0 0 33.333333%;
}

<div class="serv">
  <ul>
    <li>1</li>
    <li>2</li>
    <li>3</li>
    <li>4</li>
    <li>5</li>
    <li>6</li>
  </ul>
</div>