Google Calendar lets you export events as an ICS file for backup, migration, or importing into another app. Here's how.

Export a Single Calendar

Go to calendar.google.com on desktop (export isn't available in the mobile app)
Hover over the calendar name in the left sidebar and click the ⋮ menu
Select Settings and sharing
Scroll to Integrate calendar and click Export
Google downloads a ZIP — unzip it to find your .ics file

Export All Calendars

Use Google Takeout — deselect everything, check Calendar, then create the export. Google emails you a download link with one ICS file per calendar.

Get a Live Subscription URL

Instead of a one-time export, get a URL that always serves your latest events. In Settings and sharing → Integrate calendar, copy the Secret address in iCal format. Any app can subscribe to this URL and stay in sync — or paste it into ICS Viewer to preview it in the browser.

Keep this URL private — it gives anyone read access to your calendar without a login.