This is an update to John Utell’s 2009 post with the same title.
If the Google embedded Calendar URL something like:
https://www.google.com/calendar/embed?src=GOOGLE-USERNAME%40gmail.com&ctz=America%2FChicago%22&mode=week….
The iCal feed is
https://www.google.com/calendar/ical/GOOGLE-USERNAME%40gmail.com/public/basic.ics
Now you know.
(It should be – https://www.google.com/calendar/GOOGLE-USERNAME%40gmail.com – If only Google cared about good URL design)