Write down or copy the URL for the Google Calendar you want to add to your iPhone.
ON YOUR iPHONE: Tap the “Settings” icon, then scroll down and select “Mail, Contacts, Calendars.”
Tap “Add Account” and select “Other.”
Select the “Add Subscribed Calendar” option, fill in the Google Calendar URL in the Server box and click “Next.” Change any settings you see fit before saving the calendar. You do not need a username or password.
Toggle your view of the subscribed calendar by opening the Calendar app and tapping “Calendars” in the upper left corner. Tap a calendar name to either display or remove calendar events.