How to Change the Product Default Page Layout from 2 Columns to 3

The default layout for the product page is 2 columns: content and right. You may want to change it, so this is how it’s done:

Locate the catalog.xml file under your theme/layout folder. If you can’t find the file, copy it from the basic package.

Scroll down to the section named: <!--
Product view

There, on the first block that is nested within the <catalog_product_view> tag, locate the line: <action method="setTemplate"><template>page/2columns-right.phtml</template>

Change this line to: <action method="setTemplate"><template>page/3columns.phtml</template>

Refresh the page - you're done!