Is there a way to calculate an average in a pivot

I am trying to calculate by qtr the avg # of products included in new sales

my data is by qtr, sale name, sales area and then products and is tagged if
its a new deal

So first I tried creating a pvt and filtering on new and then counting
product name but don't know how to create an extra column to to do an
average. Some sales could have 5 products, while others 20 or even 1. Any
ideas? Thank you!!!