How to calculate how many times a customer visit a page before checking out

Make a segment for "users who checked out (visitor or Visit based)" - Visitor or Visit is based on which pool of data is required. 

Visit would show visits with checkout, while visitor will show all visits before and after checkout also. 

Then Pages report with metrics as pageView/visitor or Visits/Visitor or create calculated metric for the Avg required.

Cheers

Samrat