How to sync Google Calendar with Outlook (Microsoft 365) both ways

Updated August 2026 · the Calen1 team

Your life lives in Google Calendar — the dentist, your kid's class, Friday's flight — and your job lives in Outlook with Microsoft 365. Each one works fine on its own. The trouble starts when someone opens your work calendar, sees a gap at 4pm, and books you over something that very much exists, just on the other side.

The usual escape hatches are copying events by hand or subscribing to one calendar from the other with an ICS link. Neither survives daily use: one depends on you never forgetting, the other is read-only and always late. And when someone tries to wire up an automation instead, it almost always ends in duplicate events.

This guide explains why each shortcut falls short, what a sync actually has to do to be worth anything, and how to leave it running both ways. It works the same in reverse: work in Google Workspace, personal in Outlook.

The problem isn't having two calendars, it's that they don't talk

By default, Google Calendar and Outlook ignore each other. It isn't a bug or a misconfigured permission — they're simply two separate systems, and neither tells the other anything. That always produces the same three symptoms:

• Double bookings. You accept something at work without seeing you already had a personal commitment, or the other way round.
• Copying by hand. You end up creating the same event twice. It works until the time changes and you only update one of them.
• Fake availability. When someone looks for a slot with you, they see an incomplete calendar. Your 4pm block doesn't exist as far as they're concerned.

It gets worse if you work with outside clients, hold two jobs, or freelance with one account per project. The more accounts, the bigger the hole.

The four DIY fixes and where each one breaks

Before paying for anything, almost everyone tries one of these four. It's worth understanding exactly how far each one goes, because three of them genuinely work — just not for what you think.

1. Export an .ics and import it. In Google you go to Settings, Import and export, and download a file; in Outlook you import it. It works, but what you get is a frozen snapshot: the state of your calendar at the second you exported it. Nothing you change afterwards travels. And if you export and import again to refresh it, nothing gets replaced — everything gets duplicated. Fine for a one-time move, not for living this way.

2. Subscribe by iCal (ICS) URL. Google gives you a secret address in iCal format and Outlook adds it as an internet calendar. It's the best of the free options, because it does update on its own. But it has three hard limits: it's read-only (you can't create or edit from the other side), the refresh interval is Outlook's decision and can take hours, so you move a meeting and it sits at the old time on the other calendar for a good part of the day, and that subscribed calendar doesn't always count as busy when someone inside your company looks for a slot. Also, anyone holding that secret URL sees your entire calendar, titles and all.

3. Forward invitations to your other account. It's manual and it only covers events somebody invited you to. Your own blocks — the dentist, deep work, lunch — never travel. And when the organiser moves the meeting, the copy you forwarded stays where it was.

4. Build a flow in Power Automate (or a similar automation tool). This is where people lose the most time. A typical flow reacts to "an event was created" and makes the copy; for edits and deletions you need more flows, and for the opposite direction, several more. The underlying problem is that the flow doesn't remember which event matches which: the copy it creates on side B triggers the flow that copies from B to A, and that's how duplicates are born. Recurring series usually land as loose individual copies instead of a series, and when the connection expires everything stops silently — you find out via a missed meeting.

What a sync has to do to actually be useful

The requirements fall out of the above. Use this list to judge any tool, Calen1 included:

• Real two-way: create, edit and delete from either side and have it show up on the other.
• A memory of pairs: knowing that the work event and the personal one are the same thing, so a copy doesn't bounce back and get copied again.
• Reconciliation on connect: if you'd already copied events by hand, it should match them up, not duplicate them.
• Recurring series as series, not as twenty loose copies you can't edit.
• All-day events and time zones handled properly, especially if you travel or work with another country.
• Privacy: being able to block a slot without revealing what it's for.
• No dependence on you: if you have to press a button every morning, it isn't sync.

How to connect it with Calen1, step by step

Calen1 syncs Google Calendar and Microsoft 365 both ways: what you create, edit or delete on one side shows up on the other. The whole process takes a few minutes.

1. Create your account. No password to invent: you get in with a sign-in link sent to your email, or with Continue with Google.
2. Connect your Google account and grant the calendar permission.
3. Connect your Microsoft 365 (Outlook) account the same way.
4. Choose which calendars are included and in which direction. It doesn't have to be everything — you can leave out whatever you'd rather not mirror.
5. Let the first sync run. This is where the important part happens: Calen1 reconciles the events that already existed on both sides and pairs them up, instead of creating a second copy of each. If you'd been copying by hand, you won't end up with a duplicated calendar.
6. Run an honest test. Create an event in Google, change its time, delete it, and check Outlook. Each change lands on the other side within a couple of minutes: the engine checks roughly every two minutes. It isn't instant, and there's no point pretending otherwise.
7. Optional: add iCloud. It connects over CalDAV and you choose whether it runs one way or both. Its events land in a new, dedicated calendar called iCloud (Calen1), so they don't get mixed in with yours. Apple requires an app-specific password, which you generate at account.apple.com and which needs two-factor authentication turned on; your normal Apple password is never asked for or stored.

From then on, every copy is marked internally along with a record of which event it corresponds to on the other side. That's the detail that avoids the classic automation problem: the copy doesn't get copied again.

Privacy mode: block the slot without showing your life

Syncing personal with work has an obvious cost: suddenly your boss can read "doctor's appointment" or "lunch with Ana" on your work calendar. That's what privacy mode is for.

With privacy mode on, those events reach the work calendar as Busy and nothing else. The slot is blocked — which is all that anyone hunting for a gap actually needs — but the title and the description don't travel. You get the protection without exposing anything. It's the only sane way to mix the two worlds.

If you also want people to book you without the email ping-pong

Syncing solves the overlap. What it doesn't solve is the other drain: six emails of "does Tuesday work?" only to end up booking Thursday. For that, Calen1's Pro plan includes Agenda Pro, your own booking page, Calendly-style.

The difference is in the foundation: it only offers slots that are free across all of your connected calendars at once, not just one. That's where the sync pays off twice. On top of that:

• The guest picks their time zone and sees the times in it, with no mental arithmetic.
• The page shows in English or Spanish depending on the guest's browser.
• You decide which calendars count as busy, your working hours, the meeting length, the buffers between meetings and the minimum notice for booking.
• It's customised with your logo and your colour.

Pricing and what Calen1 doesn't do (said up front)

Prices are per user, in Mexican pesos: the Base plan costs 50 a month or 500 a year and includes syncing Google, Microsoft 365 and iCloud, privacy mode and multiple accounts. The Pro plan costs 149 a month or 1,490 a year and includes everything in Base plus Agenda Pro. The annual plan works out to paying for ten months: two are on the house.

The limits, so you don't discover them later:

• There's no free plan and no automatic free trial.
• There's no mobile app. It's a web application; you open it from the browser, on your phone too. Your events, in any case, show up in Google Calendar and Outlook exactly as always.
• The sync isn't instant: it runs roughly every two minutes.
• It only syncs calendar events. It doesn't move tasks, contacts or email.
• Today it supports Google, Microsoft 365 and iCloud. Not Yahoo, Fastmail or Nextcloud.
• There's no Slack, Teams, Zoom or Notion integration.
• There are no team features, roles or calendars shared between several users: it's built for one person's accounts.

About your data: credentials are stored encrypted, data isn't sold, and it isn't used for advertising or to train artificial intelligence models (Google's Limited Use policy is honoured). You can disconnect any account or delete yours whenever you want.

If all you want is to look at the other calendar now and then, the free ICS subscription is enough and you don't need to pay for anything. If what you want is to write on both sides, have changes and cancellations travel on their own, and stop people booking over you, that's where a real sync stops being a luxury.