The study found that the average search box is 18-characters wide. The data showed that 27% of queries were too long to fit into it. Extending the box to 27 characters would accommodate 90% of queries. Remember, you can set widths using ems, not just pixels and points. One em is the width and height of one m character (using whatever font size a website is set to). So, use this measure to scale the width of the text input field to 27-characters wide.