10 best calendar sync tools in 2026

A calendar sync tool copies events between two calendar accounts so a meeting booked in one shows up in the other. OneCal is the strongest all-round pick for keeping several Google, Outlook, and iCloud calendars in step. CalendarBridge is better when you want to control each direction separately. Reclaim.ai has the only genuinely free hosted tier. OGCS and Outlook CalDav Synchronizer are both free and open source on Windows, the second one being the way to reach iCloud or a self-hosted CalDAV server from Outlook.

If your events need to land somewhere other than a second calendar, that is a different category, and it is the last entry here.

One disclosure before the list: we build 2sync, which sits in that last category. Every other tool below was checked against its own pricing and help pages on 22 September 2026, prices are in USD, and each one carries the billing term the vendor attaches to it.

Quick comparison

Every price is the annual rate, per month, in USD.

The three kinds of tool people call a calendar sync tool

Most of the frustration in this category comes from buying the wrong kind. There are three, and they solve different problems.

• Calendar mirrors copy events from one calendar account to another so both show the same commitments. This is what people usually mean, and it is entries one through seven.
• Automation platforms run a recipe when something happens. They can move a calendar event, but each recipe runs in one direction and holds no memory of what it already copied.
• Workspace sync turns events into rows in a database, where they sit next to tasks, clients, or projects and can be edited from either side.

None of the three is a calendar app. If a better interface is what you are shopping for, the best calendar apps and Notion Calendar alternatives cover that category instead.

The question that sorts you into one of the three is not which tool is best. It is where you want to see the event: in a second calendar, in a spreadsheet-like table, or in a workflow that does something else afterward.

Before you pay: what Google and Outlook already do

Both platforms ship with sharing that covers part of this, and no tool is worth buying until you know where that stops.

Google Calendar offers five permission levels when you share with specific people (Google Calendar Help):

• See only free/busy (hide details)
• See event details
• Make changes (see private events as free/busy)
• Make changes and see event details
• Make changes and manage sharing

Sharing grants someone access to your calendar. It does not copy anything into theirs.

Outlook can subscribe to a Google Calendar over its iCal link, which gives you a read-only view that refreshes on its own. Importing instead of subscribing gives you something weaker: "The imported calendar is a static snapshot; it does not self-update" (Microsoft Support).

So the dividing line is simple. If you only need to see the other calendar, the built-in options are enough and you can stop reading. If you need your personal commitments to actually block time on your work account, where a colleague's scheduling assistant will respect them, you need something that writes events. That is what the tools below do.

Apple users have a third built-in route worth checking first, since a Google account added to iOS syncs both ways without any extra software. Our guide to syncing Google Calendar with Apple Calendar covers where that path holds and where it breaks.

1. OneCal: best for keeping several calendars in step

OneCal's differentiator is multi-way sync. Most tools copy from a source to a destination; OneCal keeps several calendars mutually current in a single sync, which is what you want when you hold three client accounts plus a personal one.

Privacy control is per sync. You can strip event titles and replace them with your own text, mark the copies private, and turn off reminder notifications on the clone so you are not alerted twice. Events can also be excluded by color or by your RSVP status.

Two limits to know. There is no free plan, only a 14-day trial with no card required. And iCloud is slower than the rest: OneCal states that iCloud updates take up to 10 minutes to appear on the other calendars, while Google and Outlook move in real time. Pricing is per user and stated in USD.

2. CalendarBridge: best for controlling each direction separately

CalendarBridge counts what it sells in sync connections, and the definition is worth understanding before you pick a plan. A connection is one ordered source-to-destination pair: a one-way sync is one connection, a two-way sync between two calendars is two, and syncing three calendars in every direction is six.

Basic includes 2 connections, Premium 20, and Pro 56. In practice that means the cheapest plan buys exactly one two-way sync between two calendars, which is the common work-plus-personal case.

Speed depends on the source. Microsoft and Google sources propagate within a minute or two; iCloud and ICS sources are polled every 5 to 10 minutes. Premium and Pro add a HIPAA business associate agreement, which matters if you are in healthcare. There is a trial, though the company does not publish its length.

3. SyncThemCalendars: best if you work inside Google Workspace

This one is not a separate web app. It installs as a Google Workspace add-on and runs beside your calendar, with an iOS app for the same account. The Workspace listing shows 23,000+ installs and 225 reviews, and it was last updated on 18 September 2026, so it is actively maintained.

Plans are counted in sync configurations rather than calendars: 5, 16, or 36 syncs, with unlimited calendars and unlimited events on every tier. Privacy controls let you hide any field behind a simple busy block, or rewrite the title, description, location, visibility, and reminders on the copy.

There is no free plan. The trial runs 14 days with no card.

4. Reclaim.ai: best free hosted option

Reclaim is a scheduling assistant that happens to include a solid calendar sync, and its free Lite plan is the most useful no-cost hosted option in this list: 1 calendar sync, 2 connected calendars, and 1 scheduling link, with no time limit.

The sync itself is genuinely two-way, and each copy can be set to free/busy only or full details. Synced blocks can be labeled as a work commitment, a personal commitment, or plain busy, which is a nicer outcome than a wall of identical "Busy" entries.

The catch is coverage. Calendar Sync supports Google and Outlook only, with no iCloud; Reclaim's own workaround is to feed iCloud into Google or Outlook first, and it warns that path can lag by hours or days.

Paid tiers mostly buy more syncs and a longer scheduling horizon. Starter is $10 per seat/month billed annually for 3 calendar syncs and an 8-week scheduling range; Business is $15 per seat/month billed annually and lifts both to unlimited and 12 weeks. If one sync is all you need, Lite stays free.

5. OGCS: best free tool for Windows and classic Outlook

Outlook Google Calendar Sync is the veteran of this category, and it is still the answer for anyone whose Outlook calendar is a desktop profile rather than a cloud account. It runs locally, needs no account with anyone, and requires neither install privileges nor a permanent connection.

It syncs in all three directions (Outlook to Google, Google to Outlook, or both ways) and it carries far more than the time slot: subject, description, location, attendees, reminders, availability, privacy, categories and colors, and recurring items. Events can be excluded by availability, privacy, title, category, or color.

Two caveats. The current stable release is v2.12.0 from January 2026, and the v3 line needed for the new Outlook for Windows app is still alpha, most recently in September 2026. And it is Windows only, with no macOS or hosted version.

6. Outlook CalDav Synchronizer: best for CalDAV servers and iCloud

The other free option for Outlook, and the one to pick when the other end is not Google. It is an Outlook plugin that speaks plain CalDAV and CardDAV, so it reaches iCloud, Fastmail, Nextcloud, ownCloud, SOGo, Zimbra, and the rest of the self-hosted world, alongside Google.

Each profile sets its own synchronization mode, conflict resolution, and interval, and a time-range filter keeps the sync to a window of past and future days. Contacts and tasks sync too, not just calendars.

It is actively maintained, with version 4.7.1 released in August 2026, and it supports Outlook 2007 through 2021 plus Microsoft 365 for desktop on .NET 4.8. Like OGCS, it is Windows-only and needs a desktop Outlook profile, so it is no help if your Outlook exists only in a browser.

7. CalendarSync: best self-hosted command-line option

This is a Go binary you configure with a YAML file and schedule yourself, built by the German consultancy inovex. It is stateless, which means the destination is reconciled against the source on every run rather than tracked in a database somewhere.

Be clear about what it copies. By default, "only the time is synced", and further fields are opt-in through transformers that can carry attendees, location, reminders, description, meeting links, and titles (inovex/CalendarSync on GitHub). Out of the box you get a privacy-preserving time blocker, not a detailed copy.

It is one-way by design, source to sink, with no iCloud and no CalDAV. The project is alive, with commits landing in September 2026, though releases went quiet for roughly 17 months between v0.10.1 and v0.11.0 in January 2026. There is no hosted scheduler either, so the sync interval is whatever your cron job says, and setup starts with creating your own OAuth client in Google Cloud or Azure and pasting the credentials into an encrypted config file. If you are weighing self-hosted plumbing more broadly, our 2sync vs n8n comparison covers the same trade between control and maintenance.

8. Zapier: best for destinations no sync tool reaches

Zapier earns its place here because it comes up in every thread about calendar sync, and because it is genuinely the right answer when your destination is a tool no sync app supports. It is the wrong answer for keeping two calendars consistent, and Zapier says so itself: "No. Zapier does not support two-way syncing between apps right now."

That line is from Zapier's own help center, which goes on to explain that you can imitate two-way sync with two opposing Zaps, then warns you not to create a Zap loop. A loop is exactly what two opposing recipes produce when each one's output looks like new input to the other.

The free plan runs 100 tasks a month on two-step Zaps, which a shared calendar will exhaust quickly. Our Zapier comparison covers what changes when the destination is a Notion database.

9. Make: best for visual multi-step workflows

Make is the same architecture with a better canvas: scenarios in place of Zaps, with routers and filters that make branching logic far easier to read. A calendar-to-calendar sync still means two scenarios, one per direction, with the same loop risk and no shared state between them.

It bills in credits, where each module action counts as one. The free plan allows 1,000 credits a month, two active scenarios, and a 15-minute minimum gap between runs; paid plans start at $9 per month billed annually for 10,000 credits and drop that gap to a minute.

Metering is the real constraint on both platforms: a busy shared calendar burns an allowance fast. If you are weighing the two against each other, we compared them in Zapier vs Make.

10. 2sync: best when events belong in a Notion database

This is the category the other nine do not cover. Instead of copying an event to a second calendar, 2sync writes it into a Notion database as an editable row you can filter, sort, and link to a client or project. It covers Google Calendar, Outlook Calendar, Todoist, Google Tasks, Gmail, and both contact books. We build it, so weigh the entry accordingly.

The direction is set per field rather than per sync. Title and time can flow both ways while the description only travels toward Notion, which is how you keep meeting notes written in Notion from overwriting an invite everyone else can see. Filters decide what qualifies in the first place, by calendar, by title, by attendee, or by any Notion property.

Among the people who set up a sync with us, 78.9% choose two-way, and the average person selects 4.13 calendars or task lists, which is the clearest signal we have that one calendar is rarely the whole picture. Google Calendar is the most connected app on the platform, at 96,484 users.

There is a version of the two-calendar problem this shape solves well. Several Google calendars fit inside a single automation, and a Google calendar plus an Outlook calendar are two automations pointed at the same Notion database, which makes the database the place both show up. The Ignore linked setting exists for exactly that setup, so a page already tied to one automation is not written twice.

Setup runs about five minutes and is covered step by step in our guides to syncing Notion with Google Calendar and syncing Notion with Outlook Calendar. Unito is the other tool worth a look in this category, priced for larger teams.

How to choose

Six things separate these tools once you get past the marketing pages.

• Direction. One-way is safer and covers most cases; two-way means an edit on either side rewrites the other. Our docs explain what changes between one-way and two-way at the field level.
• Details or busy blocks. Decide whether the copy should carry titles and attendees or simply hold the time. A copy that carries full details into a work account is visible to anyone with access to that calendar.
• Recurring events. This is where calendar sync breaks most often, because a weekly series, a single moved occurrence, and a canceled one are three different objects. Test a recurring event before you trust any tool with your week.
• Latency. Real time usually means under a minute or two for Google and Microsoft sources, and 5 to 10 minutes for iCloud and ICS feeds, whatever the homepage says.
• What the vendor stores. A hosted mirror holds an access token for both accounts and can read every event in them. A local tool like OGCS or a self-hosted binary keeps that on your machine.
• Cost as accounts multiply. Per-seat pricing, per-calendar tiers, and CalendarBridge's per-direction connections all scale differently. Price the setup you will have in a year, not the one you have today.

The work-and-personal split that sends most people looking for these tools is also worth solving upstream. Our comparison of Outlook Calendar and Google Calendar covers which one to make the primary account, which reduces how much syncing you need at all.

Conclusion

For most people running two or three calendars, OneCal or CalendarBridge will do the job, and the choice between them comes down to whether you want everything mutually current or each direction pinned down deliberately. Reclaim is where to start if you want to spend nothing. For a Windows desktop Outlook profile, OGCS handles Google and Outlook CalDav Synchronizer handles everything that speaks CalDAV.

Check the free built-in sharing first. It solves the seeing problem, and a good number of people never needed a tool at all.

And if the reason you are syncing is that your meetings should be sitting next to your tasks, your clients, or your projects, a second calendar was never going to be the answer. That is the case for putting the events in a database instead.

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