OpenCal

Guide · October 8, 2026

How to merge Google and Outlook calendar availability

Google Calendar and Outlook can show each other's calendars through an iCal subscription link. The subscription is read-only and can be hours behind. OpenCal reads Google and Outlook directly and shows the free time from both on one link.

How do I add my Google Calendar to Outlook?

Copy the calendar's “Secret address in iCal format” from Google Calendar and subscribe to it in Outlook, or connect both calendars to OpenCal. Google's steps are: open Settings, click the calendar under “Settings for my calendars”, click Integrate calendar, copy the secret address, then paste it as your other calendar app asks. In Outlook on the web, the subscription is under Add calendar, then Subscribe from web. Google warns: “Only you should know the Secret Address for your calendar. Do not share this address with other people.” Google Calendar Help: Sync your calendar with computer programs and Microsoft Support: Import or subscribe to a calendar in Outlook.com or Outlook on the web, fetched October 8, 2026.

How often does Outlook update a subscribed Google calendar?

Microsoft says a subscribed calendar can take more than 24 hours to update, while OpenCal reads each connected calendar when your page or link opens. For Outlook.com, Microsoft says: “This update can take more than 24 hours, although updates should happen approximately every 3 hours.” For Outlook on the web, Microsoft gives approximately every 6 hours. An imported .ics file never updates: “Your calendar doesn't refresh the imported events automatically.” Microsoft Support published this information on the same page, fetched October 8, 2026.

How do I add my Outlook calendar to Google Calendar?

Publish the Outlook calendar as an ICS link and add it in Google Calendar with Add other calendars, then From URL. Google says: “You can only add a calendar with a link if the other person's calendar is public.” In Outlook on the web, Publish a calendar is under Calendar settings, Shared calendars. Microsoft says an ICS link lets people subscribe to your calendar through Outlook. Google Calendar Help: Add a calendar from a URL and Microsoft Support: Share your calendar in Outlook on the web, fetched October 8, 2026.

How does OpenCal merge Google and Outlook availability?

OpenCal connects to Google and Microsoft with sign-in and reads busy times from both each time your page or link opens. You can connect several Google accounts and several Microsoft accounts. In Settings, you choose which calendars count as busy. The link shows the time that is free in all of them. OpenCal keeps each read in memory for at most one minute and never writes those busy times to its database.

Does OpenCal copy my events between Google and Outlook?

No. OpenCal reads only busy times and shows free time. It never asks for event titles, descriptions, locations or guests. When someone books a time, OpenCal keeps the booking by default. You can choose to add bookings to a Google or Outlook calendar instead.

What happens if my work Outlook calendar cannot connect?

Some companies block outside apps, and OpenCal then reads the work calendar through Settings, Other calendars. The OpenCal Sync extension for Chrome and Edge reads Outlook on the web in your signed-in browser and syncs every 15 minutes while the browser is open. Read from screen reads the Outlook or Teams desktop app when you press it and pick the window.

What does it cost?

OpenCal is free.

Get your OpenCal link

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