Google and Outlook calendar sync: iCal, Caltsu or Power Automate

The quick answer

Keeping Google and Outlook calendars in step by hand is a reliable way to miss meetings. Pick one of these instead:

1. For a view-only calendar, subscribe via URL. It's free, but updates can take a day to show up. Fine for holidays, not for your real schedule.
2. To block off your time, use a sync tool like Caltsu. It creates Busy events on the other calendar as soon as something changes, so you stop getting double-booked.
3. If you're in IT, try Microsoft Power Automate. It's flexible and comes with many Microsoft 365 plans, but you build and maintain the workflows yourself, and they break.

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You have two calendars.

Work runs on Microsoft Outlook. Your personal life, or a side business, runs on Google Calendar. They don't talk to each other.

So you book a dentist appointment on your personal calendar, and your boss books a team meeting at the same time because Outlook shows you as available. Or you miss a client call because you were looking at the wrong app.

This guide covers the free workaround, a proper sync tool and the do-it-yourself route, so you can pick the one that fits.

Why is this so hard?

Google and Microsoft compete. Neither has much reason to make its calendar work well with the other's. Each wants you to use theirs for everything.

So there's no built-in button that merges the two schedules. You have to connect them yourself, and there are two ways to do it:

1. Subscription (iCal). One calendar reads a feed from the other. It's one-way, read-only and slow.
2. Real sync through the calendar APIs. A tool copies events between calendars within seconds, and the copies block your time.

Here's how to set up both.

Method 1: the free subscription method

If you only want to see Google events inside Outlook, or the reverse, and don't need to block time, this works.

The catch is speed. Outlook refreshes subscribed calendars on its own schedule, so a meeting you add to Google at 9 AM may not show up in Outlook until the next day. That's too slow for a work calendar.

How to view your Google Calendar in Outlook

1. Open Google Calendar on your computer.
2. In the left sidebar, hover over the calendar you want to share, click the three dots and choose Settings and sharing.
3. Scroll to Integrate calendar.
4. Copy the Secret address in iCal format. Don't share this link with anyone.
5. Open Outlook on the web.
6. In the Calendar view, click Add calendar, then Subscribe from web.
7. Paste the URL and click Import.

How to view your Outlook calendar in Google

1. Open Outlook on the web.
2. Click Settings (the gear icon) > Calendar > Shared calendars.
3. Under Publish a calendar, pick the calendar and set permissions, for example "Can view all details".
4. Click Publish and copy the ICS link.
5. Open Google Calendar.
6. Next to "Other calendars", click + and choose From URL.
7. Paste the link and click Add calendar.

This is good enough for family birthdays. It won't stop anyone from double-booking you at work.

Method 2: third-party sync tools

If your boss needs to see that you're busy during a personal appointment, without learning what the appointment is, you need a sync tool.

A subscription puts a see-through overlay on your calendar. A sync tool puts real events in it that other people's scheduling tools respect.

Why use a sync tool?

• Coworkers see "Busy" instead of "Interview with another company."
• Updates arrive within seconds.
• Scheduling tools like Calendly and Outlook's Scheduling Assistant see the synced events and won't offer those slots.

How Caltsu works

We built Caltsu because we were tired of waiting a day for iCal subscriptions to catch up. We wanted something we could set up once that would keep our time blocked without showing our private lives to coworkers.

To set it up:

1. Connect accounts. Sign up and link your Google and Outlook accounts through their own sign-in pages.
2. Create a sync. Choose which calendar blocks which. For example, your personal Google Calendar blocks your work Outlook calendar.
3. Check the block title. Blocks are titled "Busy" by default. Caltsu copies the event's time to the other calendar, never its title, attendees, location or notes.
4. That's it.

Now when you add "Dentist" to your Google Calendar at 2:00 PM, Caltsu creates a Busy event on your Outlook calendar at the same time. Colleagues see you're booked, and you skip the "can we reschedule?" emails.

Other options

We think Caltsu is the most direct fix, but two other tools come up often.

• Reclaim.ai suits people who live in Google Calendar and want to schedule habits like lunch or focus time around their meetings. It's closer to a task planner than a plain sync tool.
• Zapier is the DIY route. A Zap can create a calendar event whenever another one is created. It's flexible, but each sync counts as a task, so a busy calendar gets expensive.

Method 3: the hard way (Microsoft Power Automate)

If you're an IT admin or like logic puzzles, you can build your own sync with Microsoft Power Automate, formerly Microsoft Flow.

You create a flow that watches Calendar A for new, changed or deleted events and repeats each change on Calendar B.

It has two things going for it. Many Microsoft 365 business licenses already include it, and you can customize it heavily if you know what you're doing.

It also has real problems:

• It's fragile. When an authentication token expires, the flow stops.
• Infinite loops are easy to create. An update on Calendar A triggers an update on B, which triggers one on A, and so on until you notice.
• You're the support team. When it breaks, you fix it.

Unless you want to spend weekends debugging JSON, skip this one.

Comparison: all sync methods side by side

Our recommendation

Pick based on what a missed meeting costs you.

Use the free subscription if you only need a reference. Seeing your kid's soccer schedule on your work calendar so you know when to leave is fine with iCal. A few hours of delay won't matter.

Use Caltsu if people count on you being where you said you'd be. If you run a side business, freelance, or have a busy personal life next to a corporate job, you need blocking that happens right away. For most people, the useful part is showing that you're busy without showing why.

Use Power Automate if you're a technical user automating a workflow for a whole department and you have time to maintain it.

Copying events between calendars by hand is a poor use of your time. Set up a sync once and stop thinking about it.