Increase SharePoint 2013 Lookup Column Width

Requirement: Increase SharePoint 2013 multi-lookup field width

Solution: Use CSS styles to set lookup field width in SharePoint! Here is how:

• Navigate to: http://your-sharepoint-site.com/Lists/Your-List/editform.aspx
• Click on "Site Settings" gear >> Edit Page
• Click on "Add Web Part" link and then choose "Script Editor "from "Media and Content" group
• Click on "Edit Snippet" link script editor and Paste the below CSS in it. Save and close the page.

<style>
.ms-formtable table.ms-long {
    width:600px !important;
}

.ms-formtable table.ms-long .ms-input>select {
    width:300px !important;
}
</style>

Before:

After: